Biết sina=3/4.Tính cosa,tana,cotga

Ta có:

`**` `\sin^2\alpha+\cos^2\alpha=1`

`<=>\cos^2\alpha=1-(3/4)^2`

`<=>\cos^2\alpha=7/(16)`

`<=>\cos\alpha=(\sqrt{7})/4`

`**` `\tan\alpha=(\sin\alpha)/(\cos\alpha)=((3)/(4))/((\sqrt{7})/(4))=(3\sqrt{7})/7`

`**` `\cot\alpha=(1)/(\tan\alpha)=(1)/((3\sqrt{7})/(7))=(\sqrt{7})/3`

Vậy `\cos\alpha=(\sqrt{7})/4,\tan\alpha=(3\sqrt{7})/7,\cot\alpha=(\sqrt{7})/3`