- In second quadrant sin and cosec are positive
[tex]\\ \tt\hookrightarrow sin^2\theta=1-cos^2\theta[/tex]
[tex]\\ \tt\hookrightarrow sin^2\theta=1-(\dfrac{-2\sqrt{5}}{5})^2[/tex]
[tex]\\ \tt\hookrightarrow sin^2\theta=1-\dfrac{20}{25}[/tex]
[tex]\\ \tt\hookrightarrow sin^2\theta=\dfrac{5}{25}[/tex]
[tex]\\ \tt\hookrightarrow sin\theta=\dfrac{\sqrt{5}}{5}[/tex]
[tex]\\ \tt\hookrightarrow sin\theta=\dfrac{1}{\sqrt{5}}[/tex]
