Posted by David M. on .
Use a half angle formula to determine the exact value of sin 7(pi)/12.
well, 7 pi/6 is 180 + 30 degrees
and 7 pi/6 = twice 7 pi/12
we know sin and cos of 7 pi/6
sin 7 pi/6 = -1/2
cos 7 pi/6 = -(1/2)sqrt3
so now you should be able to find the sin of 7 pi/12