For 1) Note that tan(2x)=(2tanx)/(1-tan^2x)
Your question fits this exactly -> (2tan(10))/(1-tan^2(10))=tan(2(10))=tan20
Sorry about the lack of latex - don't have time now.
It's the exact same thing, except they used the Weierstrass Substitution formula for the cosine function, instead of the tangent function, as deswa1 did above.But how would i do the next question ?
Okays Thanks !It's the exact same thing, except they used the Weierstrass Substitution formula for the cosine function, instead of the tangent function, as deswa1 did above.