Question

Prove this Identity:
tanx+tany = sin(x+y)/(cosxcosy)

Answer 1

write \[\tan x =\sin x \div \cos \] then same for tany now cross multiply u will get answer

Answer 2

Sorry I think I need a little more than that :(

Answer 3

As above but do not cross multiply, just add up the LHS and the numerator is the angle sum formula

Answer 4

even with that how would I get the denominator to match? that's the only thing that is bothering me.

Answer 5

It's just addition....?

Answer 6

well on the RHS its cosxcosy not cosx+cosy

Answer 7

eg 1/2 + 1/3 = (3+2)/2*3

Answer 8

You do see this, don't you?

Answer 9

yes I do

Answer 10

So it is coxcosy on the bottom.....

Answer 11

Yes, no?

Answer 12

ya its cosxcosy on the bottom

Answer 13

sinx/cos x + siny/cos y = (sinx cos y + cos x siny) /cosx cosy

Answer 14

Got it?

Answer 15

That was it?

Answer 16

I already said the top is the angle sum formula for sin(x+y)

Answer 17

I was thinking that the denominator was cosx+cosy. So I always got stuck.

Answer 18

Ah, OK......:-)

Answer 19

Thanks for the clearing that up :)

Answer 20

ur welcome