If α\alphaα and β\betaβ are complementary angles (sum to 90°90°90°), prove that sin(α)=cos(β)\sin(\alpha) = \cos(\beta)sin(α)=cos(β).
False; this is not true for complementary angles
True; this is the cofunction identity
True; but only for acute angles
True; but the roles of sine and cosine could be reversed