A local naturalist says that a triangular area on the north side of a pond is a turtle habitat. The lengths of the sides of this area are 15 meters, 25 meters, and 36 meters. Which expression gives the measure of the angle between the sides of the habitat that measure 15 meters and 25 meters?

Answer 1

If the angle is θ, the law of cosines says that

36^2 = 15^2 + 25^2 - (2)(15)(25) cosθ