HP persamaan sin 4x – cos 2x = 0, utk 0′ =< x =< 360' adalah… ' drjt

Sin(2x+2x)  = cos 2x
sin (2x+2x) = sin2xcos2x + cos2xsin2x = (y/r . x/r) + (x/r.y/r) = 2(xy/r²)
2(xy/r²) = x/r
2y/r = 1
sin 2x = 1/2
sin positif di kuadran 1 dan 2 (x = 15 dan x = 165)

sin4x = sin60
sin 2x = sin 30
sin 4x – cos 2x = 1/2√3 – 1/2√3 = 0

sin4x = sin 660 = sin 300 = -sin60 = -1/2√3
cos2x = cos 330 = cos 30 = 1/2√3
sin4x – cos2x = -1/2√3 – 1/2√3 = -√3    salah

MAKA X = 15"