Question

Write the expression as either the sine, cosine, or tangent of a single angle.

cos(π/3)cos(π/5) + sin(π/3)sin(π/5)

Answer 1

`\cos\frac\pi3\cos\frac\pi5+\sin\frac\pi3\sin\frac\pi5=\cos\left(\frac\pi3-\frac\pi5\right)=\cos(2\pi)/(15)`