sin2x=1−cos2x2\sin^{2}x=\frac{1-\cos{2x}}{2}sin2x=21−cos2x
cos2x=1+cos2x2\cos^{2}x=\frac{1+\cos{2x}}{2}cos2x=21+cos2x
tanx2=sinx1+cosx=1−cosxsinx\tan{\frac{x}{2}}=\frac{\sin{x}}{1+\cos{x}}=\frac{1-\cos{x}}{\sin{x}}tan2x=1+cosxsinx=sinx1−cosx