bantu jawab nomer 3 sama 4

3 ga ngerti blom bljr suku banyak
4. cos 2x = cos^2x-sin^2x= 2cos^2x-1
2cos^2 x- 2cosx =0
2cosx(cosx-1)
2cos x = 0
cos x = 0
cos x = 270°,90°
cos x = 1
cos x= 0°,360°