The law of cosines
Answers are for parents and teachers.
1
b = 7, c = 8, ∠A = 60°. What is a²?
57
2
b = 5, c = 3, ∠A = 120°. Find a.
7
3
In a triangle with sides 7, 8, 9, what is the cosine of the angle opposite 9?
2/7
4
A parallelogram has sides 3 and 8 and an angle of 60°. Find the length of its shorter diagonal.
7
5
Why is the law of cosines called a generalisation of the Pythagorean theorem?
When the angle is 90° the extra term vanishes and a² = b² + c² remains.