# Homework Help: Trigonometry equatation

1. Nov 10, 2008

### ming_RICE

Sorry but i dont know how to use latex yet or to add mathematical symbols somehow.

1. The problem statement, all variables and given/known data

Prove that 1-sin2θ/cos2θ = 1-tanθ/1+tanθ

2. Relevant equations

sin2θ = 2tanθ/1+tan2θ and cos2θ =1-tan2θ/1+tan2θ

I have allready proved from a previous exercise those two above so i pressume they may be useful.

3. The attempt at a solution

1-sin2θ/cos2θ = 1-2tanθ/1+tan2θ/1-tan2θ/1+tan2θ=

i then multiply the fraction with (1+tan2θ) and i am left with

1-2tanθ/1-tan2θ

i have tried various things but i suppose this is the way to go.. maybe not, i dont know, i am stuck. Can someone help me on that one please?

2. Nov 10, 2008

### marlon

Prove that (1-sin2θ)/cos2θ = (1-tanθ)/(1+tanθ)
------------------------------------------------------------

just replace the sine and cosine by the relevant equations that you cited.

The exercise is quite straighforeward.

you should come to (1-tanθ)^2/(1-tan^2(θ))

marlon

3. Nov 10, 2008

### ming_RICE

Yes you told me exactly what i did :uhh:
but for some reason i am stuck at this step. Its not that straight forward for me as it is for you :grumpy:

4. Nov 10, 2008

### marlon

Again i tell you : redo what you did because you calculated it incorrectly. What you give as your result is already incorrect ! Recalculate the substitutions

ps : please, try to be polite to people that are trying to help you. Otherwise you won't last long here. Just a small piece of advice.

5. Nov 10, 2008

### ming_RICE

Ok so my calculations were wrong i will try and work it out then, thanks.

And btw i admire that you are helping people with their math problems but you did not help me with your first post, capito?

6. Nov 10, 2008

### marlon

If i didn't help you with my post then why do you say your calculations are wrong ?

We are not gonna spoon feed the solution to you. That doesn't serve ANY purpose.
I clearly stated what equation you should get if you did it properly and i also told you where your mistakes were made.

Aside, giving you the solution, there is not much else to say

marlon

7. Nov 10, 2008

### ming_RICE

You said that my calculations were wrong in your second post ... In your first post however you just said what i said, you sounded like a parrot.

8. Nov 10, 2008

### ming_RICE

ok sorry i just read the post again you are right i am just a little dizzy to much math for me those days.... :)

9. Nov 11, 2008

### marlon

So, is the problem solved ?

marlon

10. Nov 15, 2008

### ming_RICE

Yes problem solved