SAT Math Problem (25)

Question

If (cos x)(sin x) = .2, what is the value of (cos x + sin x)² ?

Answer 1

(cos x + sin x)² = cos²x + sin²x + 2(cos x)(sin x)

 

but cos²x + sin²x = 1 (pythagorean identity)

 

so the answer is 1 + 2 x .2 = 1.4