Khan Academy
Khan Academy: Proof of Heron's Formula (1 of 2)
Sal proves Heron's Formula for finding the area of a triangle solely from its side lengths.
Khan Academy
Khan Academy: Ca Geometry: More on Congruent and Similar Triangles
Worked examples of similar and congruent triangles.
Khan Academy
Khan Academy: Triangle Similarity & the Trigonometric Ratios
Sal explains how the trigonometric ratios are derived from triangle similarity considerations.
Khan Academy
Khan Academy: Geometry Word Problem: A Perfect Pool Shot
Sal uses triangle similarity to plan the perfect shot in a pool game.
Khan Academy
Khan Academy: Trig Word Problem: Stars
Sal solves a word problem about the distance between stars using the law of cosines.
Khan Academy
Khan Academy: Solving for a Side With the Law of Cosines
Learn how to use the law of cosines to find the missing side length of a triangle when given two side lengths and the contained angle measure.
Khan Academy
Khan Academy: Proof of the Law of Cosines
Sal gives a simple proof of the Law of cosines.
Sophia Learning
Sophia: Equilateral Triangle Interior Angles Practice Problems: Lesson 2
This lesson will provide practice problems that involve solving for unknown angle and side measures of equilateral triangles. It is 2 of 5 in the series titled "Equilateral Triangle Interior Angles Practice Problems."
Sophia Learning
Sophia: Equilateral Triangle Interior Angles Practice Problems: Lesson 3
This lesson will provide practice problems that involve solving for unknown angle and side measures of equilateral triangles. It is 3 of 5 in the series titled "Equilateral Triangle Interior Angles Practice Problems."