A) sin(5π/2 + α) = sin(π/2 + α) = sin(π/2)cos(α) + cos(π/2)sin(α) = 1cos(α) + 0sin(α) = cos(α)
B) cos(3π + α) = cos(π + α) = -cos(α)
C) sin(7π/2 - α) = sin(3π/2 - α) = -cos(α)
A) sin(5π/2 + α) = sin(π/2 + α) = sin(π/2)cos(α) + cos(π/2)sin(α) = 1cos(α) + 0sin(α) = cos(α)
B) cos(3π + α) = cos(π + α) = -cos(α)
C) sin(7π/2 - α) = sin(3π/2 - α) = -cos(α)