Question

I don't understand the last step, can someone please explain.​

Answer 1

Step-by-step explanation:

in second last line the derivation of sinx is written as cosx

so,the equation has become

2sinx cosx

and 2sinx cosx is actually an identity

I.e.2sinx cosx=sin2x

that's why in last line it is replaced by sin2x

also there are two 2sinx cosx so they are taken common and then written as:

(x^2-1)2sinx cosx