The Law of Cosines
Unknown Grade45 min
Learning Objective
I can solve real-world problems involving triangles by applying the Law of Cosines to determine unknown side lengths or angles.
Lesson Flow
Watch Video
Law of cosines | Trig identities and examples | Trigonometry | Khan Academy
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Practice
7 questions • Short answer
Exit Ticket
“A triangle has sides measuring 15 units and 20 units, with an included angle of 60°. Calculate the length of the third side using the Law of Cosines. Show all work. In a triangle, the lengths of two sides are 9 units and 12 units, and the angle between them is 45°. Determine the length of the third side using the Law of Cosines. Show all work. ”
Teacher Guide
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