Angles of tiles

Question

An interior designer plans to use triangular tiles that are 8 cm × 9 cm × 13 cm for a backsplash. In order to fit them together properly, she needs to know the size of the angles on the tile. Calculate the three angles on the tile, accurate to one decimal place.

Answer 1

Start with the Law of Cosines:

9² = 8² + 13² - 2(8)(13) cos θ (angle opposite 9 cm side.)

Use the same Law for one other or use Law Sines.