## anonymous 5 years ago Use identities (no calculators) to find the exact value for cos(pi/2)cos(pi/6) - sin(pi/2)sin(pi/6)

ho ho ho this one is $cos(a+b)$ $a=\frac{\pi}{2}, b=\frac{\pi}{6}, a+b=\frac{2\pi}{3}$ $cos(\frac{\pi}{3})=\frac{1}{2}$