Question #400f1

1 Answer
Mar 6, 2017

sqrt(2 - sqrt3)/2232

Explanation:

Use unit circle, trig table , and property of complement arcs.
sin ((11pi)/12) = sin (-pi/12 + pi) = sin (pi/12)sin(11π12)=sin(π12+π)=sin(π12)
Evaluate sin (pi/12)sin(π12) by using trig identity:
2sin^2 a = 1 - cos 2a2sin2a=1cos2a.
In this case,
2sin^2 (pi/12) = 1 - cos (pi/6) = 1 - sqrt3/2 = (2 - sqrt3)/22sin2(π12)=1cos(π6)=132=232
sin^2 (pi/12) = (2 - sqrt3)/4sin2(π12)=234
sin (pi/12) = +- sqrt(2 - sqrt3)/2sin(π12)=±232.
Sine sin (pi/12)sin(π12) is positive, take the positive value.
Finally, sin ((11pi)/12) = sin (pi/12) = sqrt(2 - sqrt3)/2sin(11π12)=sin(π12)=232