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# Trig Proof help needed

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1. Tried different substitutions but im assuming i've done them incorrectly so just need some guidance on the most appropriate one to use.
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2. (Original post by GGHarambe)
Tried different substitutions but im assuming i've done them incorrectly so just need some guidance on the most appropriate one to use.
use double angle formulas. Post what you've tried. Specifically: and [tex]\sin 2A = 2\sin A\cos A/tex].
3. (Original post by GGHarambe)
Tried different substitutions but im assuming i've done them incorrectly so just need some guidance on the most appropriate one to use.
Final answer is not a double angle, so the first step is to use double angle formulae for sine and cosine then manipulate it from there.
4. (Original post by GGHarambe)
Tried different substitutions but im assuming i've done them incorrectly so just need some guidance on the most appropriate one to use.
You know that tan A = sin A / cos A so that tells you to use the version of cos 2A that has just sin A in it (and be careful with the signs when you remove the brackets).
5. (Original post by Zacken)
use double angle formulas. Post what you've tried. Specifically: and [tex]\sin 2A = 2\sin A\cos A/tex].
1-(1-2sin^2)/sin 2A

-2Sin^2/Sin 2A

-2sin^2/SIN A Cos A + Sin A Cos A
6. (Original post by GGHarambe)
1-(1-2sin^2)/sin 2A

-2Sin^2/Sin 2A

-2sin^2/SIN A Cos A + Sin A Cos A
You expanded wrong, . Check it again.

Denominator looks good.
7. (Original post by RDKGames)
You expanded wrong, it should be . Check it again.
Thanks
8. (Original post by RDKGames)
You expanded wrong, . Check it again.

Denominator looks good.
How come it's not 2Sin^2 ?
9. (Original post by GGHarambe)
How come it's not 2Sin^2 ?
Huh?
10. (Original post by RDKGames)
Huh?
originally you put +Sin^2 and i'm where has the 2 in front gone
11. (Original post by GGHarambe)
originally you put +Sin^2 and i'm where has the 2 in front gone
Simple error that I fixed and you came back too quickly for.
12. (Original post by RDKGames)
Simple error that I fixed and you came back too quickly for.
Oh okay my bad. Thought I was going insane.
13. (Original post by GGHarambe)
1-(1-2sin^2)/sin 2A

-2Sin^2/Sin 2A

-2sin^2/SIN A Cos A + Sin A Cos A
I did say be careful with the signs when you remove the brackets!

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