Multiply and simplify cos alpha sin alphacos alpha sin alp

Multiply and simplify. (cos alpha - sin alpha)(cos alpha + sin alpha) (cos alpha - sin alpha)(cos alpha + sin alpha) = (Simplify your answer.)

Solution

(cosa - sina)(cosa + sina)

This is iof the form (a-b)(a+b)
which is a^2 - b^2

which is given by (cosa)^2 - (sina)^2

cos^2(alpha) - sin^2(alpha) ------> ANSWER

IF this does not work,
try cos(2*alpha) ----> ANSWER