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# Trig indentities Watch

1. Use the identity sin^2(x)+cos^2(x)=1 to rewrite the equation sin^2(x)=2cos^2(x)-1 in terms of cos(x).

The answer is 3cos^2(x)=2 but I don't know how to get there, can anyone help me please? (x)=theta

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2. (Original post by joem8197)
Use the identity sin^2(x)+cos^2(x)=1 to rewrite the equation sin^2(x)=2cos^2(x)-1 in terms of cos(x).

The answer is 3cos^2(x)=2 but I don't know how to get there, can anyone help me please? (x)=theta

Posted from TSR Mobile
sin^2(x)+cos^2(x) = 1

so

sin^2(x) = 1 - cos^2(x)
3. Using the identity what does sin^2(x) = ?
4. Thanks for replying bus this still doesn't make any sense, what do I need to use the identity for?

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5. (Original post by joem8197)
Thanks for replying bus this still doesn't make any sense, what do I need to use the identity for?
To replace the

And you needed to substitute for the
6. Ahh right I get it now thank you!

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Updated: April 13, 2013
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