Math Is Fun Forum

  Discussion about math, puzzles, games and fun.   Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ • π ƒ -¹ ² ³ °

You are not logged in.

#1 2012-10-20 14:43:54

woweycowey
Member
Registered: 2012-10-20
Posts: 1

Please Help with this Trigonometry Proof!

If anyone could help with this that would be amazing, im just finding myself stuck.


(sinxcosx)/((cosx^2)-(sinx^2))  =  ((tanx)/(1-tanx^2))

Offline

#2 2012-10-20 20:00:48

Bob
Administrator
Registered: 2010-06-20
Posts: 10,058

Re: Please Help with this Trigonometry Proof!

hi woweycowey

Welcome to the forum!

I think you mean sin^2 (x) rather than sinx^2 ie.

Anyway start with the left hand side:

Divide top and bottom by

and it comes out straight away.

Bob


Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob smile

Offline

#3 2012-10-21 02:25:30

zetafunc.
Guest

Re: Please Help with this Trigonometry Proof!

Bob bundy's way is the best way since it is only one step. Here is another neat way to do it but it takes a bit longer (it's how I did it though);

I still prefer the one-step method though, haha. So this post is a little redundant...

#4 2012-10-21 03:24:07

Bob
Administrator
Registered: 2010-06-20
Posts: 10,058

Re: Please Help with this Trigonometry Proof!

hi zetafunc,

That's what I thought as well to start with.  I think the double angle formulas jump out at you.

But I  thought the OP might not have met them so I looked to see if I could bypass them.  The tan2A formula comes from dividing by cos so I tried that instead and nearly fell off my chair.

Good to offer a choice so not redundant.  smile

Bob


Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob smile

Offline

Board footer

Powered by FluxBB