Question

My cousin needs help with this please help thanks

Answer 1

A.
`\cos \: x - 4 \: \cos \: x \: { \sin}^(2)x` (first option)

Explanation:

➡️
`\cos(x + 2x)`

➡️
`\cos \: x \: { \cos}^(2) x - \sin \: x \: { \sin }^(2) x`

➡️
`\cos \: x(1 - 2 \sin^(2)x) - \sin \: x * 2 \sin(x) \cos(x)`

➡️
`\cos(x) - 2 \sin^(2) x \cos(x) - 2 \sin^(2) x \cos(x)`

➡️
`\cos(x) - 4 \cos(x) \sin^(2) x`