1.

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

Answer» We have `7 cos^(2) theta+3 sin^(2) theta=4`
`rArr 7(1- sin^(2) theta)+3 sin^(2) theta=4`
or `4 sin^(2) theta=3`
or `sin^(2) theta =3/4=((sqrt(3))/2)^(2)`
or `sin^(2) theta="sin"^(2) pi/3`
or `theta= npi pm pi/3, n in Z`


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