What is sin 2pi/3? How do you solve without a calculator?

Hello,

sin 120°=-sin 60°=-√3 / 2 = - 0,8660 ...

To solve the expression sin 2pi/3, we can convert first 2pi/3 into degrees. pi is equal to 180, hence 2pi/3 is equal to 120 degrees. 120 degrees is located in the second quadrant in which the terminal angle equivalent is 60 degrees. Using special triangle 30-60-90, sin 120 is equal to sqrt 3 over 2.