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Solve 7cos^2theta+3sin^2theta=4...

Solve `7cos^2theta+3sin^2theta=4`

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`7cos^2theta+3sin^2theta=4`
`4cos^2theta+3cos^2theta+2sin^2theta=4`
`4cos^2theta+3=4`
`4cos^2theta=1`
`cos^2theta=1/4`
`costheta=pm1/2`
`theta=npipmpi/3`.
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