Question

A triangle has sides A, B, and C. Sides A and B are of lengths `2` and `5`, respectively, and the angle between A and B is `(5pi)/8`. What is the length of side C?

Answer 1

5,73

Explanation:

Use the cosine law in this situation. The cosine law states the following for ANY triangle.
`c^2 =a^2 + b^2 -2ab*cos(Y)`
With Y= angle between a and b.

So `Y=(5*pi)/8`

If the angle is nice and the cosine gives a value displayed in pi, the senses is much nicer. For this calculation one cannot simplify it.