Unit Plan
Cuemath

Cuemath: Median of a Triangle

For Students 9th - 10th Standards
This lesson explores the equation of the median of a triangle formula, sum of medians of a triangle, altitude of a triangle, median of equilateral triangle formula, and median of a triangle definition while discovering the interesting...
Lesson Plan
Illustrative Mathematics

Illustrative Mathematics: G C Circumcenter of a Triangle

For Teachers 9th - 10th Standards
The goal of this task is to construct the circumcenter of a triangle, that is, the point which is the same distance from each of the triangle's three vertices. This task shows that the three perpendicular bisectors of the sides of a...
Lesson Plan
Illustrative Mathematics

Illustrative Mathematics: G Srt Joining Two Midpoints of Sides of a Triangle

For Teachers 9th - 10th Standards
In this task, students must prove that angles and triangles are congruent and that a parallel line passes through the midpoints of two sides of the larger triangle. Aligns with G-SRT.B.4.
Handout
Math Open Reference

Math Open Reference: Interior Angles of a Triangle

For Students 9th - 10th
Learn about the interior angles of a triangle with this helpful reference tool. Provides a detailed definition and interactive activity that enhances further explanation. Includes links to related topics.
Unit Plan
Mathigon

Mathigon: Geometry: Angles and Polygons: Drawing Triangles

For Students 9th - 10th Standards
This lesson focuses on the Triangle Inequality, when the sum of the lengths of any two sides of a triangle is greater than the length of the third. When this happens, the three sides cannot form a triangle.
Activity
Analyze Math

Analyze Math: Medians of Triangle

For Students 9th - 10th Standards
The properties of the medians of a triangle are explored using an interactive geometry applet.
Lesson Plan
Illustrative Mathematics

Illustrative Mathematics: G Gpe Scaling a Triangle in the Coordinate Plane

For Teachers 9th - 10th Standards
The goal of this task is to apply dilations to a triangle in the coordinate plane. Young scholars will need to find the coordinates of a point which cuts a given segment into one third and into two thirds. The two dilated triangles share...
Unit Plan
Cuemath

Cuemath: 30 60 90 Triangle

For Students 9th - 10th
In this lesson, learn all about the 30-60-90 triangle. Learn about its sides, its area, and the rules that apply to these triangles. Includes simulations and practice questions.
Unit Plan
Cuemath

Cuemath: Triangle Inequality Theorem

For Students 9th - 10th
This lesson explores triangle inequality theorem, triangle inequality theorem-proof, and triangle inequality theorem problems. Try the hands-on triangle inequality theorem calculator and interactive problems to have a better...
Interactive
National Council of Teachers of Mathematics

Nctm: Illuminations: Making Triangles

For Students Pre-K - 1st Standards
Understand the mathematical meaning of a triangle and the idea of congruence, or sameness, in geometry.
Activity
Ministry of Education and Universities of the Region of Murcia (Spain)

Ministerio De Educacion Y Ciencia: Triangulos

For Students 9th - 10th
In Spanish. This interactive activity shows how to compute the area of a triangle and the concept of altitude, median and angle bisector. [Requires Java.]
Handout
Wolfram Research

Wolfram Math World: Equilateral Triangle

For Students 9th - 10th Standards
MathWorld goes into detail about equilateral triangles at this site. Use this site to find out how to construct an equilateral triangle using a compass and straight edge. Learn about the altitude of such triangles, and the rationality of...
Interactive
Calculator Soup

Calculator Soup: Law of Sines Calculator

For Students 9th - 10th Standards
Use the law of sines to calculate unknown angles or sides of a triangle. In order to calculate the unknown values, you must enter 3 known values.
Unit Plan
Cuemath

Cuemath: Coordinate Geometry

For Students 9th - 10th Standards
A comprehensive guide for learning all about Coordinate geometry with definitions, the coordinate plane, formulas, equation of a line, related topics, solved examples, and practice questions.
Lesson Plan
Illustrative Mathematics

Illustrative Mathematics: G Gpe Equal Area Triangles on the Same Base I

For Teachers 9th - 10th Standards
This task is a relatively easy application of the formula for the area of a triangle and the use of parallel lines. Aligns with G-GPE.B.5.
Handout
Science Struck

Science Struck: List of Different Types of Geometric Shapes

For Students 4th - 8th Standards
A comprehensive list of 2D shapes and 3D solids with everything from a triangle to a dodecahedron. Includes illustrations and short descriptions of attributes for each.
Unit Plan
Cuemath

Cuemath: Law of Cosine

For Students 9th - 10th Standards
Explore the world of the Law of Cosine in this mini-lesson. Provides a definition, simulations, examples, and practice questions that help with understanding.
Lesson Plan
Illustrative Mathematics

Illustrative Mathematics: G C Right Triangles Inscribed in Circles I

For Teachers 9th - 10th Standards
This task provides a good opportunity to use isosceles triangles and their properties to show an interesting and important result about triangles inscribed in a circle with one side of the triangle a diameter. The fact that these...
Lesson Plan
Illustrative Mathematics

Illustrative Mathematics: G Co Midpoints of Triangle Sides

For Teachers 9th - 10th Standards
The goal of this task is to use similarity transformations to relate two triangles. The triangles are obtained by taking midpoints of two sides of a given triangle. Aligns with HSG-CO.C.10.
Unit Plan
Khan Academy

Khan Academy: Dilate Triangles

For Students 9th - 10th Standards
Given a figure and a definition of a dilation, draw the image. Students receive immediate feedback and have the opportunity to try questions repeatedly, watch a video or receive hints.
Graphic
Shodor Education Foundation

Shodor Interactivate: Coloring Multiples in Pascal's Triangle

For Students 9th - 10th
In this activity, the student can visually identify number patterns in Pascal's triangle by coloring multiples of a given number.
Handout
University of St. Andrews (UK)

University of St. Andrews: Biography of Hero

For Students 9th - 10th
This University of St. Andrews site contains information on the life of Heron as well as his accomplishments.
Interactive
Calculator Soup

Calculator Soup: Equilateral Triangles Calculator

For Students 9th - 10th Standards
An equilateral triangle is a special case of a triangle where all 3 sides have equal length and all 3 angles are equal to 60 degrees.
Lesson Plan
Illustrative Mathematics

Illustrative Mathematics: G Srt Mt. Whitney to Death Valley

For Teachers 9th - 10th
In this task, students are asked to make a mathematical model and determine if it is possible to see a point on the surface of the Earth that is 85 miles away, and well below sea level, from the top of a mountain. The curvature of the...

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