Question

#3 Write each in terms of sin x

a) cos²x

b) 3 sin²x - 4 cos²x

Answer 1

`\boxed{sin^(2)x + cos^(2)x = 1}`

a)
`cos^(2)x = 1 - sin^(2)x`

b)
`3sin^(2)x - 4cos^(2)x = 3sin^(2)x - 4(1 - sin^(2)x) = \\`

`= 3sin^(2)x - 4 + 4sin^(2)x = 7sin^(2)x - 4`