Sinx1 + cosx = 1-cosx, cos2x+ 3sinx . cosx - 1 = 0

a.$\frac{\mathrm{sinx}}{1+\mathrm{cosx}}$=1-cosx
b.${\cos }^{2}x$ + 3sinx.cosx - 1 = 0
c.cosx + $\frac{1}{4}$ sinx = ${\cos }^{3}x$ 
d.2${\sin }^2$(X+$\frac{\mathrm{\pi }}{4}$)=2${\cos }^{2}x$+cotx