Question

Choose the correct alternative:

If sin θ = `3/5`, then cos θ = ?

Options

• `5/3`

• `3/5`

• `4/5`

• `5/4`

Answer 1

`4/5`

cos θ = `sqrt(1 - sin^2 θ)`

∴ cos θ = `sqrt(1 - (3/5)^2)`

∴ cos θ = `sqrt(1 - (9/25))`

∴ cos θ = `sqrt(16/25)`

∴ cos θ = `4/5`.