wonk holor: mtk membingungkan

Aturan kosinus

$p^{2}=\left (c+d \right )^{2}=a^{2}+b^{2}-2.a.b.cos\left ( \alpha +\beta \right )$

$a^{2}+b^{2}-(c^{2}+2.c.d+d^{2})=2.a.b.cos\left ( \alpha +\beta \right )$

$\left (a^{2}-c^{2} \right )+\left (b^{2}-d^{2} \right )-2.c.d=2.a.b.cos\left ( \alpha +\beta \right )$

$\left (t^{2}\right )+\left (t^{2}\right )-2.c.d=2.a.b.cos\left ( \alpha +\beta \right )$

$2t^{2}-2.c.d=2.a.b.cos\left ( \alpha +\beta \right )$

.....kedua ruas dibagi 2.a.b

$cos\left ( \alpha +\beta \right )=\frac{t}{a}.\frac{t}{b}-\frac{c}{a}.\frac{d}{b}$

${\color{Blue} cos\left ( \alpha +\beta \right )=cos\: \alpha.cos\: \beta - sin\: \alpha.sin\: \beta}$

wonk holor