If y=sin−1(x√1−x+√x√1−x2) then dydx=
sin(tan−1x),|x|<1, is equal to a) x√1−x2 b) 1√1−x2 c) 1√1+x2 d) x√1+x2
If f(x)=x−x2+x3−x4+.......∞,|x|<1, then f′(x)=