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# A2 Maths: Core 3 Proving Identity - Help watch

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1. Hi

I am reading an example Q:

How do they get from line 2 to line 3?

I multiplied the numerator and denominator by cosxsinx and didn't get what they have on the third line :/

Probably a minor error from me..could someone write it out to explain possibly?

Thank you

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2. (Original post by Yusufff)
Hi

I am reading an example Q:

How do they get from line 2 to line 3?

I multiplied the numerator and denominator by cosxsinx and didn't get what they have on the third line :/

Probably a minor error from me..could someone write it out to explain possibly?

Thank you

Posted from TSR Mobile
Bit of a nasty one to be honest.

Consider the numerator first. If you multiply everything by sincos, then both denominators dissapear and you get sin * sin + cos * cos = 1.

But since you've multiplied that by that in the numerator, you also have to do so in the denominator, which gives sin + cos this time.
3. I figured out my silly error with the help of your post - thanks so much!

(Original post by SeanFM)
Bit of a nasty one to be honest.

Consider the numerator first. If you multiply everything by sincos, then both denominators dissapear and you get sin * sin + cos * cos = 1.

But since you've multiplied that by that in the numerator, you also have to do so in the denominator, which gives sin + cos this time.

Posted from TSR Mobile

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Updated: September 10, 2016
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