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# Identities watch

1. 3cos^2x+sin^2x+5sinx=0

If sin^2x+cos^2x=1

Then wouldnt this be 3+5sinx=0?
2. No, sorry - because .
3. (Original post by Smaug123)
No, sorry - because .
Ty.
4. (Original post by Tynos)
3cos^2x+sin^2x+5sinx=0

If sin^2x+cos^2x=1

Then wouldnt this be 3+5sinx=0?
There is both sine and cosine function in the equation.
The solution will more simple if there is only sine or cosine functions in this equation.
From the identity you wrote
cos^2x=1-sin^2x
SUb this in cos^2x and you will get a quadratic equation for sinx
For sinx you can use the formula for quadratic equations.

where a,b,c is the factor of proper sine-power or constant.

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Updated: May 15, 2013
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