jika tan [tex]2 \alpha + \frac{4}{ \tan( \alpha ) } = 0[/tex] maka salah satu nilai [tex] \cos( \alpha ) [/tex] adalah..

[tex]2 \alpha + \frac{4}{ \tan( \alpha ) } = 0 \\ \\ \frac{4}{ \tan( \alpha ) } = - 2 \alpha \\ \\ \frac{1}{ \tan( \alpha ) } = - \frac{1}{2} \alpha \\ \\ \tan( \alpha ) = - 2 \alpha \\ \\ \frac{ \sin( \alpha ) }{ \cos( \alpha ) } = \frac{ - 2 \alpha }{1} \\ \\ \cos( \alpha ) = \frac{ - 2 \alpha }{ \sqrt{4 { \alpha }^{2} + 1 } } \\ \\ \cos( \alpha ) = \frac{ - 2 \alpha + \sqrt{4 { \alpha }^{2} - 1 } }{4 \alpha {}^{2} + 1 } [/tex]

Mencari Cosa dengan segitiga

Jadi, sisi miring = √(4a² +1)