The Law of Cosines
Unknown Grade•45 minutes
Learning Objective
I can solve real-world problems involving triangles by applying the Law of Cosines to determine unknown side lengths or angles.
Practice Questions
This lesson includes 7 practice questions to reinforce learning.
View questions preview
1. Explain the Law of Cosines and describe how it differs from the Pythagorean theorem.
2. Given a triangle with sides B = 10 units, C = 15 units, and an angle θ = 60°, use the Law of Cosines to find the length of side A.
3. A triangle has sides measuring 8 units and 6 units, with an included angle of 45°. Calculate the length of the third side using the Law of Cosines.
...and 4 more questions
Educational Video
Law of cosines | Trig identities and examples | Trigonometry | Khan Academy
Khan Academy