**find exact value of cos (9pi/4) How do you get(pi/4 + 2pi)**

**Answer:**

9π/4 = π/4 + 8π/4 = π/4 + 2π … so π/4 is the reference angle … 45º

cos(π/4) = √2 / 2

**find exact value of cos (9pi/4) How do you get(pi/4 + 2pi)**

**Answer:**

9π/4 = π/4 + 8π/4 = π/4 + 2π … so π/4 is the reference angle … 45º

cos(π/4) = √2 / 2