Question

bài 1: Cho biết sinx = 1/3. Tính cosx, cotx, tanx

bài 2: Cho biết tanx = 3. Tính cotx, sinx, cosx

 

Answer 1

Bài 1: 

\(cosx=\sqrt{1-\dfrac{1}{9}}=\dfrac{2\sqrt{2}}{3}\)

\(tanx=\dfrac{1}{2\sqrt{2}}=\dfrac{\sqrt{2}}{4}\)

\(cotx=2\sqrt{2}\)

 

Answer 2

Bài 2 : tan x = 3 \(\Rightarrow cotx=\dfrac{1}{3}\)

\(1+tan^2x=\dfrac{1}{cos^2x}\Rightarrow1+9=\dfrac{1}{cos^2x}\)  \(\Rightarrow cosx=\pm\dfrac{1}{\sqrt{10}}\)

cos x = \(\pm\dfrac{1}{\sqrt{10}}\Rightarrow sinx=\pm\dfrac{3}{\sqrt{10}}\)