geometry tutoring


Math Tutors

Cornerstone Protection IconCornerstone Protection

836 Euclid Avenue Suite 16, Lexington

5.0 37 reviews

  • Avatar Larry Barton ★★★★★ a month ago
    Amazing assistance provided by Shannon today on my security system. I’m so grateful for your prompt, efficient, professional, and courteous service. Put me down as a customer for life!
  • Avatar Megan Haller ★★★★★ 2 months ago
    One of the most painless experiences I've had. They came on time and was over the moon professional with still keeping a level of personability to it. The gentleman also went out of his way to say that my husband and Mines business … More was appreciated. Which is actually rare to be appreciated by such a great company. So thank you and we look forward to continuing services with this company.
  • Avatar Megan Magsam ★★★★★ 3 months ago
    I am so happy we decided to go with cornerstone. They were quick and efficient. Shannon and the installer we very friendly. We got a lot of equipment and it was still within our budget. 10/10 would definitely recommend! Thank you
  • Avatar Collins Youngblood ★★★★★ 2 weeks ago
    Love the customer service and Shanon and his team go above and beyond for my restaurant. Couldn't of asked for a better security system and level of service that his team provides.
  • Avatar kanu patel ★★★★★ 2 months ago
    I have been using Cornerstone Protection service for over 5 years and I'm really happy with the service and state-of-the-art equipments and it's futures are so much in advance and friendly, I highly recommend Cornerstone Protection … More Service any and all business that need a security protection days and nights specially after business hours(Cornerstone Protection is perfect solution for your business). Owner of Cornerstone Protection is proactive with their customers and their equipments. Good experienced with Cornerstone Protection!!!
    Kanu Patel
  • Avatar Liz Jones ★★★★ 8 months ago
    We had a very positive experience with Alissa as a tutor for our pod of 5th grade boys from January - June 2020. She cared a lot about the boys and worked hard to create meaningful activities for them. The pod experience was invaluable … More for all of our families during a difficult year and we were so grateful to have found this partnership! We also want to appreciate Craig for helping to match us with a tutor on very short notice after we had cycled through a few folks who were not able to see the commitment through. Thanks for sticking with us!
  • Avatar S CL ★★★★★ 11 months ago
    Dusty was the exact person we needed to help our child finish out the school year. So grateful to him for the way he steadily encouraged her and helped her stay on track and organized. He is flexible, responsive to our needs/schedule as … More a family, and a delight to be with. We are also thankful that Craig at Themba Tutors really "gets it" and partnered us with such a wonderful tutor who was a great fit for our girl.
  • Avatar Nicole May ★★★★★ 11 months ago
    My child worked with Gillian D virtually for math enrichment. She is an excellent teacher. She took time to understand my child's specific learning style and provided tools that would be engaging. She was kind and empathetic- really … More made it her goal to connect with my child and build trust and rapport. My child started the school year with confidence and without the typically "brain-drain" that occurs over the summer, thanks to Gillian.
  • Avatar Gillian Davidoff ★★★★★ 11 months ago
    I am going into my second year as a Themba tutor. I have met so many great individuals while working for this company. Craig and the rest of the Themba team do such an excellent job picking and choosing Themba tutors that suit each client's … More individual needs! I look forward to meeting new tutors and clients in the 2021-2022 school year!
  • Avatar carolina luttmann ★★★★★ 11 months ago
    Our son started in a new high school, 100% remote, and was really struggling with Latin and Physics. I found Themba Tudors online and had an initial call with Craig, who was very knowledgeable, responsive, and found 2 amazing tutors for … More us. Both the Latin and the physics tutors were fantastic, connected with my son really well and helped him go from 'failing' grade to 'honors'! I will for sure continue using (and recommending!) Themba Tutors. Thank you, C, K, and W!
  • Avatar Eric Fingerman ★★★★★ 10 months ago
    Brian is a fantastic executive functioning coach. Super helpful, flexible with hours, and tailored the experience to our needs.
  • Avatar Susan Wong ★★★★★ a year ago
    Giulia Mercuri is a great Italian tutor! She was very responsive and accessible. Giulia put a ton of effort into preparing for each session and really helped our son with test preparation and projects. We are grateful that she was able … More to help, especially since our son did not receive any live teaching during COVID. We are happy that she was referred to us!
  • Avatar Christine Gennetti ★★★★★ a year ago
    As an adult student diagnosed with a learning disability during grad school, I knew I needed help dealing with my Master's program's demanding workload. I was seriously considering dropping out when I was referred to Themba Tutors. … More I was paired up with a wonderful tutor, Julie, who was a total lifesaver. I learned many techniques that I can utilize in the future as I embark on the next phase of my career.
    I can wholeheartedly say after working with Themba for two years that I would not have finished my program without this organization. And I am so thankful I selected them.
  • Avatar Fabiola FITZPATRICK ★★★★★ 2 years ago
    We were introduced to a wonderful tutor: Mcedwyn. He and our son, a freshman in college, worked well together. As a result, our son’s grades significantly improved. The tutor taught our son subject content and various methods to effectively … More study for quizzes and exams. Our son was also taught time management and organization. My son’s experience with the tutor made the first year of college a less intimidating experience.
  • Avatar Jude Eugene ★★★★★ a year ago
    We have been with our tutor, Cailin Schiller, for two years, from 5th - 7th grade. She started as an executive functioning tutor with my daughter. From the start, she demonstrated a depth of expertise and a selective use of techniques skillfully … More adapted to my daughter’s ADHD and Math disability. Cailin made Math accessible and understandable to her in a way that even her teachers had not been able to do. She differentiated reading, writing and math tasks and assignments to tailor them to my daughter’s unique learning differences. Not only did it have an effect on her grades and her work efficiency, but she finally could do her work with less anxiety. Even my daughter’s teachers used Cailin’s guidance to modify their work with her. But most importantly, she became my daughter’s favorite resource. I can’t say how invaluable Cailin has been to my daughter’s progress and well-being. I’d recommend her a million times over. She is a gem.
  • Avatar Janice Eidus ★★★★★ a year ago
    Victoria is a superb tutor. She helped my high school age daughter with her writing. Victoria's skills as a tutor, as well as her sense of humor and her engaging personality went a long way with my daughter.
  • A Google User ★★★★★ 3 years ago
    I'm so glad we were referred to Themba Tutors. After a great initial conversation to learn our needs, we were connected with an excellent tutor, Felicia, who is helping our high school daughter learn better organizational and executive … More skills. Highly recommended.
  • Avatar Fara Jones ★★★★★ 3 years ago
    Themba Tutors provided a leaning specialist that was a perfect fit for my daughter. I told them what we were looking for and they delivered. Our tutor is responsive and flexible and makes it easy for my daughter to reach out to her own … More her own, which gives her an added sense of responsibility over her learning. As a therapist myself, I now regularly recommend Themba to my patients. A much needed and well provided service to the community!!
  • Avatar Frances Simpson ★★★★★ 3 years ago
    The tutors at Themba are fantastic! Caitlyn McNeill helped our son academically, but also with getting organized in every subject, which he so desperately needed. She offered great advice and useful strategies that helped our son become … More a more successful student. We are using Themba tutors again this year for our daughter. We're so happy to have been referred to them!
  • Avatar Mary Jean Babic ★★★★★ 3 years ago
    I'm so glad we were referred to Themba Tutors. After a great initial conversation to learn our needs, we were connected with an excellent tutor, Felicia, who is helping our high school daughter learn better organizational and executive … More skills. Highly recommended.
  • Avatar Nina Herman ★★★★★ 3 years ago
    We had a wonderful experience with our tutor Micaela. She helped our son not only academically but at every level. We will be forever grateful to have her in our lives.
  • Avatar Frances ★★★★★ 3 years ago
    The tutors at Themba are fantastic! Caitlyn McNeill helped our son academically, but also with getting organized in every subject, which he so desperately needed. She offered great advice and useful strategies that helped our son become … More a more successful student. We are using Themba tutors again this year for our daughter. We're so happy to have been referred to them!
  • Avatar Michael Birnbaum ★★★★★ 3 years ago
    Paul Smith at Themba has been an exceptional tutor for my son, both in terms of teaching the subject matter and teaching how best to approach the process of learning math and executing assignments. We feel very fortunate to be working with … More Paul.
  • Avatar Monica Alzate ★★★★★ 3 years ago
    We were very lucky to have found Edwouine Swift, my son's therapist through Themba Tutors. Thomas is 12 years old, and it is extremely difficult to get him to write. Edwouine just works her magic with him, he adores her and is so … More eager to follow her guidance. I have no doubt she will be a positive driving force in his academic future.

Top Math Tutors in Brooklyn



Our GEOMETRY tutors travel to YOUR home:

Brooklyn Manhattan Queens Staten Island The Bronx

We also travel to:

Westchester New Jersey (NJ) Connecticut Long Island

Module 1: Plane Geometry

Topic A: Introduction to Geometry

Plane Geometry is about flat shapes like lines, circles, and triangles … shapes that can be drawn on a piece of paper.
Point, Line, Plane and Solid
A Point has no dimensions, only position
A Line is one-dimensional
A Plane is two dimensional (2D)
A Solid is three-dimensional (3D)

Plane Geometry is all about shapes on a flat surface (like on an endless piece of paper).GEOMETRY TUTORING


geometry tutoring

Let us start with a point. A point has no dimensions.
A point really has no size at all! But we show them as dots so we can see where they are.

Now let’s allow the point to move in one direction. We get a line. geometry tutoring
We need just one value to find a point on that line. So we have one dimension. A line is one-dimensional.

Now let’s allow the point to move in a different direction. geometry tutoringAnd we get a plane. We need two values to find a point on that plane. So we have two dimensions, or “2D”.
Circles, triangles, squares, and more are plane shapes.

We let that point move in another completely different direction, and we have three dimensions. geometry tutoring
Spheres, cubes, cylinders, and more are 3-dimensional or “3D”. We also call them solid shapes.

geometry tutoringThe world we live in is 3D.
We can have more dimensions (such as this 4D Tessaract) in mathematics, but they are hard to draw!



2D Shapes

A polygon is a plane (2D) shape with straight sides. To be a regular polygon, all the sides and angles must be the same:

geometry tutoring

Triangle – 3 Sides


Heptagon – 7 Sides

geometry tutoring

Square – 4 Sides


Octagon – 8 Sides

geometry tutoring

Pentagon – 5 Sides


Nonagon – 9 Sides

geometry tutoring

Hexagon – 6 sides


Decagon – 10 Sides

Other Common Polygons

These are 2D shapes, and they are polygons, but not regular polygons:


Any 4-sided 2D shape


Rectangle – 4 Sides
All right angles

Curved Shapes

These are also 2D shapes but are not polygons because they have curves:


A triangle is a polygon with three edges and three vertices. It is one of the basic shapes in geometry. A triangle with vertices A, B, and C is denoted \triangle ABC. In Euclidean geometry, any three points, when non-collinear, determine a unique triangle and simultaneously, a unique plane. It can be classified into three: Equilateral, Isosceles, and Scalene.

There are three special names given to triangles that tell how many sides (or angles) are equal. There can be 3, 2, or no equal sides/angles:


Equilateral Triangle
Three equal sides; Three equal angles, always 60°


Isosceles Triangle
Two equal sides; Two equal angles


Scalene Triangle
No equal sides; No equal angles

How to remember? Alphabetically they go 3, 2, none:

  • Equilateral: “equal”-lateral (lateral means side) so they have all equal sides
  • Isosceles: means “equal legs”, and we have two legs, right?   Also isosceles has two equal “Sides” joined by an “Odd” side.
  • Scalene: means “uneven” or “odd”, so no equal sides.


What Type of Angle?

Triangles can also have names that tell you what type of angle is inside:


Acute Triangle
All angles are less than 90°


Right Triangle
Has a right angle (90°)


Obtuse Triangle
Has an angle more than 90°

Combining the Names

Sometimes a triangle will have two names, for example,

GEOMETRY TUTORINGRight Isosceles Triangle
Has a right angle (90°), and also two equal angles

Topic B: Perimeter

Perimeter is the distance around a two-dimensional shape.

Example: the perimeter of this rectangle is 7+3+7+3 = 20

GEOMETRY TUTORINGExample: the perimeter of this regular pentagon is:


3 + 3 + 3 + 3 + 3 = 5×3 = 15

The perimeter of a circle is called the circumference:
Circumference = 2π × radius



Perimeter Formulas

Perimeter = a + b + c


Perimeter = 4 × a
a = length of sideGEOMETRY TUTORING

Perimeter = 2 × (a + b)


Perimeter = a + b + c + d


Circumference = 2πr
r = radius

Perimeter = r(θ+2)
r = radius
θ = angle in radians

Perimeter = very hard!

Topic C: Area


Area is the quantity that expresses the extent of a region on the plane or a curved surface. The area of a plane region or plane area refers to the area of a shape or planar lamina, while surface area refers to the area of an open surface or the boundary of a three-dimensional object.


Area = ½ × b × h
b = base
h = vertical height

Area = a2
a = length of side


Area = w × h
w = width
h = height


Area = b × h
b = base
h = vertical height

Area = ½(a+b) × h
h = vertical height


Area = π × r2
r = radius

Area = πab


Area = ½ × r2 × θ
r = radius
θ = angle in radians


Note: h is at right angles to b

Example: What is the area of this rectangle?


The formula is:
Area = w × h
w = width
h = height

We know w = 5 and h = 3, so:
Area = 5 × 3 = 15
Example: What is the area of this circle?


Radius = r = 3
= π × r2
= π × 32
= π × (3 × 3)
= 3.14159… × 9
= 28.27 (to 2 decimal places)

Example: What is the area of this triangle?


Height = h = 12
Base = b = 20

Area = ½ × b × h = ½ × 20 × 12 = 120

Word Problem:
Example: Sam cuts grass at $0.10 per square meter How much does Sam earn cutting this area:


Let’s break the area into two parts:


Part A is a square:
Area of A = a2 = 20m × 20m = 400m2
Part B is a triangle. Viewed sideways, it has a base of 20m and a height of 14m.
Area of B = ½b × h = ½ × 20m × 14m = 140m2
So the total area is:
Area = Area of A + Area of B = 400m2 + 140m2 = 540m2

Sam earns $0.10 per square meter
Sam earns = $0.10 × 540m2 = $54




High School Mathematics Teacher Completing Master’s Thesis and transitioning into his Doctoral Research at Teachers College, Columbia University



Certified Math and Special Education Teacher, MS Math Education



Master’s in STEM Education and Master’s in Applied Math



Bachelor’s degree in Secondary Education with a Concentration in Mathematics, M.S. in General and Special Education (grades 1-6)



Master of Philosophy and Doctor of Philosophy, Master of Educational Leadership



Master’s in Elementary Education, Bachelor’s in Political Science & French


Master’s in Leadership in Math Education, Bachelor’s Degree in Mathematics



M.A degree in Clinical Psychology

Chat with Themba Tutors Today!
Our Geometry Tutors work with all skill levels, travel to you, and offer remote tutoring services


Call: (917) 382-8641, Text: (833) 565-2370 


(we respond to email right away!).

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Craig Selinger, CEO of Themba Tutors (serving Manhattan, Brooklyn, Queens, Staten Island, Bronx, Westchester, Long Island, New Jersey, and Connecticut), is a NY State licensed speech-language pathologist, executive functioning coach, and learning specialist with over 18 years of experience working professionally with over a thousand families. His expertise includes language-based learning issues, e.g. reading, writing, speaking, and listening, executive functioning, ADHD/ADD, and learning disabilities. Check out his interviews with top-notch professionals in the field on Spotify.
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