# Math Is Fun Forum

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

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## #1 2010-11-13 03:18:51

Natkirky
Member
Registered: 2006-10-17
Posts: 21

### Trig Identities

Hi,

I was wondering if someone could help with this question:

Show:  1 - cosθ/sinθ = sinθ/1 + cosθ

I can get all other variations of this to work and i can only get this to work the wrong way around ie 1 + cosθ/sinθ, so I know it's something really stupid I am missing.

I would be grateful for any help or tips

Thanks Natkirky

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## #2 2010-11-13 04:15:08

mathsyperson
Moderator
Registered: 2005-06-22
Posts: 4,900

### Re: Trig Identities

Here's an intermediate step:

Why did the vector cross the road?
It wanted to be normal.

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## #3 2010-11-13 05:38:56

Natkirky
Member
Registered: 2006-10-17
Posts: 21

### Re: Trig Identities

Hi Mathsyperson,

Thanks for the step got that to work out now.  I always use the denominator to multiply by did not even think to use this.

Thanks again

Natkirky

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## #4 2010-11-13 09:35:54

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

### Re: Trig Identities

Hi Natkirky;

Or:

This is a proportion so you can cross multiply:

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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