jawabanyan ya kakak buruan

Ingat rumus trigonometri berikut
[tex]1) \tan( \beta )^{2} = \sec^{2} ( \beta ) - 1 \\ 2) \sec( \beta ) = \frac{1}{ \cos( \beta ) } [/tex]
Maka
[tex] \frac{ (\tan\beta)^{2} }{1 + \sec( \beta ) } = 1 \\ \frac{ \sec^{2} ( \beta ) - 1 }{1 + \sec( \beta ) } = 1 \\ \frac{ (\sec( \beta ) + 1)( \sec( \beta ) - 1) }{ \sec( \beta ) + 1} = 1 \\ \sec( \beta ) - 1 = 1 \\ \sec( \beta ) = 1 + 1 \\ \sec( \beta ) = 2 \\ \frac{1}{ \cos( \beta ) } = 2 \\ 2 \cos( \beta ) = 1 \\ \cos( \beta ) = \frac{1}{2} [/tex]
Cos beta yg bernilai 1/2 adalah cos 60°
Maka beta nya adalah 60°

Semoga dapat dipahami