Question

find the exact (nondecimal) value of sin(13pi)

Answer 1

Rule: sin(n*pi) = 0

where n is any integer

Answer 2

the most common you are probably familiar with are

sin(0*pi) = sin(0) = 0

sin(1*pi) = sin(pi) = 0

sin(2*pi) = sin(2pi) = 0