If sin A + cos A = 1/3 and A ∈ {0, π/2}, then what is sin 2A?
Show answer & explanation
Correct answer: C
Explanation
(sin A + cos A)² = sin²A + cos²A + 2sinA cosA
(1/3)² = 1 + 2sinA cosA
1/9 = 1 + 2sinA cosA
2sinA cosA = 8/9
sin 2A = 2sinA cosA
sin 2A = 8/9