sin2x = cos(x+30)
when x=120,
sin 240 = cos 150
There are other values, but you have to solve a 4th-degree equation to get them.
2sinx cosx = cos30 cosx - sin30 sinx
square both sides, collect terms, convert sin^2 = 1-cos^2, and square both sides again. Gets messy
Solve for x if sin2x=cos(x+30) for x [-180;180]
1 answer