Two planes leave an airport at the same time. Their speeds are 130 miles per hour and 180 miles per hour, and the angle between their courses is 48°. How far apart are they after 1.5 hours?

Answer 1

This is a straight application of the law of cosines.

You are looking for the side opposite an angle 48° in a triangle with sides adjacent to the 48° angle equal to 180*1.5 and 130*1.5 respectively.

The law of cosines is c² = a² + b² - 2ac*cos ∠C.

You plug in the numbers and do the arithmetic!