Câu hỏi của Nguyễn Thư

Question

Cho cos α =$\frac{4}{5}$. Tìm sin α, tang α.

Võ Hồng Phúc · Accepted Answer

Ta có :$Sin^2\alpha+Cos^2\alpha=1$

$\Leftrightarrow Sin^2\alpha+\frac{16}{25}=1$

$\Leftrightarrow Sin^2\alpha=\frac{9}{25}$

$\Leftrightarrow Sin\alpha=\frac{3}{5}$

$\Rightarrow tan\alpha=\frac{Sin\alpha}{Cos\alpha}=\frac{\frac{3}{5}}{\frac{4}{5}}=\frac{3}{4}$Câu trả lời: Ta có :$Sin^2\alpha+Cos^2\alpha=1$

$\Leftrightarrow Sin^2\alpha+\frac{16}{25}=1$

$\Leftrightarrow Sin^2\alpha=\frac{9}{25}$

$\Leftrightarrow Sin\alpha=\frac{3}{5}$

$\Rightarrow tan\alpha=\frac{Sin\alpha}{Cos\alpha}=\frac{\frac{3}{5}}{\frac{4}{5}}=\frac{3}{4}$

Công chúa vui vẻ · Answer

Ta có: $\sin^2\alpha+\cos^2\alpha=1$

$\Leftrightarrow\sin^2\alpha=1-\cos^2\alpha$

$\Leftrightarrow\sin^2\alpha=1-\left(\frac{4}{5}\right)^2$

$\Leftrightarrow\sin^2\alpha=\frac{9}{25}$

$\Leftrightarrow\sin\alpha=\frac{3}{5}$

Ta lại có: $\tan\alpha=\frac{\sin\alpha}{\cos\alpha}$

$\Leftrightarrow\tan\alpha=\frac{3}{\frac{5}{\frac{4}{5}}}$

$\Leftrightarrow\tan\alpha=\frac{3}{4}$

Chúc bạn hok tốt!!! Nguyễn ThưCâu trả lời: Ta có: $\sin^2\alpha+\cos^2\alpha=1$