Question

The angle lies in Quadrant II.
sin0=3/4
What is cos 0?

Answer 1

cosФ is
`-(√(7))/(4)` ⇒ B

Explanation:

Let us solve the question using one of the identities of trigonometry

∵ sin²Ф + cos²Ф = 1

∵ sinФ =
`(3)/(4)`

→ Substitute it in the rule above to find cos Ф

∴ (
`(3)/(4)`)² + cosФ² = 1

∴
`(9)/(16)` + cosФ² = 1

→ Subtract
`(9)/(16)` from both sides

∴ cos²Ф =
`(7)/(16)`

→ Take √ for both sides

∴ cosФ = ±
`(√(7))/(4)`

∵ Angle Ф lies on the second quadrant

∴ cosФ is a negative value

∴ cosФ =
`-(√(7))/(4)`

∴ cosФ is
`-(√(7))/(4)`