Here's the question you clicked on:
kittycat01
need help in calculus http://www.wolframalpha.com/widget/widgetPopup.jsp?p=v&id=f4ccdf86d504bc91f8652fa6d7b76db6&title=Derivative%20Calculator&theme=blue&i0=1st&i1=tan^-1%28%28a%2Bx%29%2F%281-ax%29%29&podSelect=&includepodid=Input&podstate=Input__Step-by-step%20solution&showAssumptions=1&showWarnings=1 tan^-1((a+x)/(1-ax)) using substitution method differentiate it :'( what should i substitute to get the answer ?????
i think i have to subtitute x with acos2theta
*phew* finally done it :)
lol @hartnn there is a formula tan^-1 x+ tan^-y = (x+y)/(1-xy)