May 2018

The equation says, sin2x=2sinxcosx
=2tanx/1+tan^2x
... How did they get 2tanx/1+tan^2x?

Here's my question:
Example: examine the function
Y=x(x-1)^3
Y'=3x(x-1)^2+(x-1)^3=(x-1^2(4x-1)
Y"=4(x-1)^2+2(x-1)(4x-1) ... How did they get 4(x-1)^2+2(x-1)(4x-1)?

Can you help me about problem 126