(cos(2x)-cos(4x))/(cos(2x)+cos(4x)) how does this fraction turn into (-2sin(3x)sin(-x))/(2cos(3x)cos( can you do a step by step proof to show how the 1st expression turns into the second expression?

Which of the expressions (on the photo document i inserted) together represent all solutions to the following equation? 8cos(12x)+4=-4 *the answer should be in degrees.* > i would like for someone to explain the process to find the solutions for this.

Two cars which are 40 miles apart start moving simultaneously in the same direction with constant speeds. if the speed of the car which is behind is 56 mph and the speed of the other car is 48 mph, how many hours will it take for the car which is behind to catch up the car ahead of it?

Varies inversely with x. if y=8.5 when x=-1 find x when y=-1