Cos(x+y)cos(x-y)=cos^2y - sin^2x

What is the ratio of the length of an object in yards to the length of the same object in miles?

When a 757 passenger jet begins its descent to the ronald reagan national airport in washington, d.c., it is 3900 feet from the ground. its angle of descent is 6 degrees. how far must the plane fly to reach the run way? a. 37,106 ft b. 37,310.4 ft c. 23,456.6 ft d 2,492.7 ft

Solve the equation for b: a= (1/2)(b)(h)