If sin θ=2/3 and θ is an acute angle, what is the value of cos²θ−sin²θ?
Show answer & explanation
Correct answer: B
Explanation
Given:
sinθ = 2/3
θ is an acute angle
By the formula:
sin²θ + cos²θ = 1
sin²θ = (2/3)²
= 4/9
cos²θ = 1 − 4/9 = 5/9
cos²θ − sin²θ
= 5/9 − 4/9
= 1/9