Maths help (trigonometry) +REP

[Matthew]

Hiya

I'm completely stumped with this one. Its about proving identities.

You need to prove the following identity (take = to be the 'is identical to' sign):

1/sinx - sinx = cosx/tanx

I think I'm on the right lines, but get stuck at a point?

I do the following (hopefully this makes sense as its hard to read when fractions are written out on a computer as x/y IMO :()

1/sinx - sinx = cosx/tanx

1/sinx - sinx = 1-sin2x/sinx

1-sin2x/sinx = cos2x/sinx

where do I go from here? I'm now up to cos2x/sinx = cosx/tanx

Thanks if anyone can help lol, I bet its easy and I'm just being an idiot though :(

[Chippiewill]

you're basically there, cos^2(x)/sinx = (cosx/sinx) * cosx = 1/tanx * cosx = cosx/tanx

You probably didn't notice that

cosx / sin x = 1/tanx

Since that's just

sinx/cosx = tanx flipped upsidedown.

[Matthew]

you're basically there, cos^2(x)/sinx = (cosx/sinx) * cosx = 1/tanx * cosx = cosx/tanx

You probably didn't notice that

cosx / sin x = 1/tanx

Since that's just

sinx/cosx = tanx flipped upsidedown.

ah right, makes sense :)

Thanks, +REP! :D

[efq]

I am astonished you guys can stand that sort of Mathematics. That would stress me out to the point I would actually want to go jump off a bridge.

[Mr-Trainor]

I am astonished you guys can stand that sort of Mathematics. That would stress me out to the point I would actually want to go jump off a bridge.
I've just finished C3 trig, and it really is the most annoying part of core maths imo :(. I've never liked trig though, even at GCSE. Stats is much easier :P.

[Chippiewill]

I've just finished C3 trig, and it really is the most annoying part of core maths imo :(. I've never liked trig though, even at GCSE. Stats is much easier :P.
You won't be thinking that after C4 differential equations ;)

[Matthew]

You won't be thinking that after C4 differential equations ;)

haha. Did you do further maths by the way? :)

[Chippiewill]

haha. Did you do further maths by the way? :)

Did? Doing.

[Mr-Trainor]

You won't be thinking that after C4 differential equations ;)
I can't wait! lol. I just hope there's the easy sections as well as the hard ones :P.

[Wig44.]

Hiya
1-sin2x/sinx = cos2x/sinx


I just wanted to point out that this is essentially the end of the proof:

1-sin2x = cos2x because sin2x + cos 2x = 1, hence cos2x/sinx, which can then be written as cosx/tanx