How do you evaluate sin(pi/4) ?

##(sqrt2)/2##
Convert ##pi/4## into degree value by multiplying it to ##180/pi##. You’ll get 45.
Sin45 = ##(sqrt2)/2##
You may apply the SOH-CAH-TOA for this one given a 45-45-90 triangle wherein the legs are 1 unit and the hypotenuse is ##sqrt2## (through Pythagorean).