Prove that cos(x+y) +cos(x-y) =2cos x cos y

Consider the diagram. which line segment has the same measure as st? rx tx sr xs

The function ƒ is defined by ƒ(x) = (x + 3)(x + 1). the graph of ƒ in the xy-plane is a parabola. which interval contains the x-coordinate of the vertex of the graph of ƒ?

Me! last question, and i'm stuck! write the algebraic expression that models the word phrase. the product of 2 divided by the number h and 8 more than the number k