identities

[Guest laalltheway]

having some trouble with proving identities, problem is:

sec2x = sec^2(x) / 2-sec^2(x) and the second one is

tany = sin2y / 1+cos2y

much help is appreciated

[greentea]

start with the definition of sec and tan in terms of sin, cos

then all that you need are the identities for double angles of sin and cos

[Guest laalltheway]

which side should i start with the left or the right?

[DQW]

I would start from the right side and use the half-angle formulae instead.

[Primarygun]

I would start from the right side and use the half-angle formulae instead.

I start from the left-hand side by using double angle formula then divide both side by (cosx)^2