Cho sinα + cosα = 3/2 Tính sinα * cosα sin^3 α + cos^3 α

`· (sin \alpha + cos \alpha)^2 = 9/4`

`1 + 2sin\alphacos\alpha = 9/4`

`sin\alphacos\alpha = 5/8`

`· sin^3 \alpha + cos^3 \alpha `

`= (sin\alpha + cos\alpha)^2 – 3sin\alphacos\alpha ( sin\alpha + cos \alpha)`

`= 9/4 – 3 . 5/8 . 3/2`

`=-9/16`