Lesson Plan
Illustrative Mathematics

Area of a Trapezoid

For Teachers 7th - 9th Standards
Here is a straightforward example of how to apply the Pythagorean Theorem to find an unknown side-length of a trapezoid. Commentary gives additional information on proving that the inside of the trapezoid is a rectangle, but is...
Lesson Plan
Curated OER

Medians and Altitudes of Triangles

For Teachers 10th
For this geometry worksheet, 10th graders determine if a given segment is a median or altitude of a triangle and use then find the indicated missing length or equation of a line.  The two page worksheet contains twenty...
Lesson Plan
Curated OER

Special Segments in a Triangle

For Teachers 10th
In this geometry worksheet, 10th graders review the vocabulary associated with the special segments of a triangle and the associated points of concurrency and solve problems in which they find the indicated missing angle or...
Lesson Plan
Curated OER

Finding the Area of an Equilateral Triangle

For Teachers 9th - 11th Standards
The problem seems simple: find the area of the equilateral triangle whose sides are each length 1. In fact, this same problem is solved in 8th grade, addressing a different Common Core standard, using the formula for area of a triangle...
Instructional Video6:29
Corbett Maths

Pythagoras Rectangles and Isosceles Triangles

For Students 7th - 12th Standards
When does the Pythagorean Theorem come in handy? An intriguing video uses the Pythagorean Theorem to solve problems other than simply finding the length of a side of a right triangle. Pupils find the diagonal of a rectangle and the...
Lesson Plan
EngageNY

Law of Sines

For Teachers 11th - 12th Standards
Prove the Law of Sines two ways. The ninth segment in a series of 16 introduces the Law of Sines to help the class find lengths of sides in oblique triangles. Pupils develop a proof of the Law of Sines by drawing an altitude and a second...
Assessment
Concord Consortium

Always, Sometimes, Never

For Students 9th - 10th Standards
Do your learners always, sometimes, or never remember the properties of the segments in triangles? Get that number closer to always with a creative lesson analyzing all four segments. Scholars consider a statement about one of the...
Worksheet
Mt. San Antonio Collage

Isosceles Triangles and Special Line Segments

For Students 9th - 12th Standards
Under which conditions can a triangle be classified as isosceles? High schoolers practice identifying isosceles triangles and special line segments, including angle bisectors, medians of triangles, and perpendicular bisectors of sides of...
Worksheet
Curated OER

Triangle Fundamentals Multiple Choice

For Students 7th - 12th
In this triangles worksheet, students identify the parts of a triangle.  They determine the value of an angle measurement, and identify the characteristics of triangles.  This two-page worksheet contains 10 problems.  This...
Lesson Plan
Illustrative Mathematics

Same Base and Height, Variation 2

For Teachers 5th - 7th Standards
This is a good model for learners to visualize triangles of the same base and height. They can can begin to comprehend that these triangles will have the same area no matter how the triangle is drawn. It is part of a series of resources...
Worksheet
Curated OER

Tricky Triangle

For Students 9th - 12th
In this triangle worksheet, high schoolers solve 1 word problem about the lengths of a triangle. Students determine the length of the longest side given the ratio of the angle measures.
Worksheet
Curated OER

Special Right Triangles

For Students 10th
For this special right triangles worksheet, 10th graders solve 9 different problems related to measuring various types of right triangles. First, they find the values of x and y in each right triangle shown. Then, students find the...
Worksheet
Curated OER

Triangles

For Students 10th
In this triangles worksheet, 10th graders solve 3 extensive informal geometry problems that involve triangles. First, they sketch a triangle, selecting 3 of the sides and constructing 3 midpoints. Students then draw each of 3 medians by...
Worksheet
Curated OER

Section 6.1-6.2 Precalculus: Trigonometry

For Students 9th - 12th
In this trigonometry worksheet, students solve 15 triangle problems.  Students use the law of sines and law of cosines to find the missing angles and side lengths of a triangles.
Worksheet
Curated OER

Parts of Similar Triangles

For Students 10th
In this parts of similar triangles worksheet, 10th graders solve 6 different problems related to determining the value of various parts of similar triangles. First, they find the value of x in the 2 figures shown. Then, students find the...
Worksheet
Curated OER

Parts of Similar Triangles

For Students 10th
In this parts of similar triangles worksheet, 10th graders solve and complete 15 different statements related to naming the parts found in similar triangles. First, they identify each definition stated that describes an everyday usage of...
Worksheet
Curated OER

Right Triangles

For Students 10th
In this right triangles worksheet, 10th graders solve and complete 12 various types of problems. First, they solve for x given each of the right triangles shown. Then, students determine the length of the shorter diagonal given the...
Worksheet
Curated OER

Special Segments is a Triangle

For Students 10th
In this geometry worksheet, 10th graders examine the special segments that occur in a triangle.  The three page worksheet contains twenty-five problems.  Answers are not included. 
Lesson Plan
Curated OER

Isosceles Triangle Theorem

For Teachers 8th - 10th
For this geometry worksheet, young scholars differentiate between regular triangles and isosceles triangles. They apply the converse theorem and the vertex angle. There are eleven questions with an answer key.
Worksheet
Curated OER

Lengths of Horizontal and Vertical Line Segments

For Students 5th - 7th
Use this lengths of horizontal and vertical line segments practice worksheet to have learners sharpen their problem solving skills as they solve six story problems.
Worksheet
Curated OER

Special Segments in Triangles

For Students 10th
In this special segments in triangles worksheet, 10th graders solve 6 various types of problems related to determining types of segments found in triangles. First, they find a segment if the line parallel is a median or an altitude....
Worksheet
Curated OER

Value of Triangles

For Students 9th - 10th
In this geometry worksheet, students identify the missing sides and angles of triangles. They find the midsegment of each triangle. There are nine questions with an answer key.
Worksheet
Curated OER

Chapter 5 Final Review Extra Problems. Triangles

For Students 10th - 12th
In this triangles activity, students identify the median, altitude, segment, angle bisector, perpendicular bisector and triangle midsegment of triangles.  They find the perimeter of triangles.  This three-page activity...
Assessment
Concord Consortium

Divisions

For Students 7th - 12th Standards
Divide and conquer the geometry problem. Young scholars consider how to subdivide triangles into smaller ones that have equal areas. They must apply their knowledge of medians to help accomplish the task.