Question

Answer 1

Ta có:
`Cos^2 alpha + Sin^2 alpha = 1`

`=>(3/5)^2 +  Sin^2 alpha = 1`

`=>9/25 + Sin^2 alpha = 1`

`=>  Sin^2 alpha = 16/25`

`=>Sin alpha = 4/5`

`=>A`

Answer 2

Ta có: \(\sin^2\alpha+\cos^2\alpha=1\)

`=>` \(\cos^2\alpha=1-\left(\dfrac{3}{5}\right)^2=1-\dfrac{9}{25}=\dfrac{16}{25}\)

`=>` \(\cos\alpha=\sqrt{\dfrac{16}{25}}=\dfrac{4}{5}\)

Chọn A