1. Buktikan bahwa: sec A + tan A = cos A / 1-sin A

Trigonometry Identity.

[tex]\displaystyle \boxed{a-b=\frac{(a-b)(a+b)}{a+b}=\frac{a^2-b^2}{a+b}}[/tex]

From right side to left side:
[tex]\displaystyle \frac{\cos A}{1-\sin A}\\ =\frac{\cos A}{\frac{1-\sin^2 A}{1+\sin A}}\\ =\frac{\cos A}{\frac{\cos^2 A}{1+\sin A}}\\ =\frac{1+\sin A}{\cos A}\\ =\frac{1}{\cos A}+\frac{\sin A}{\cos A}\\ =\sec A+\tan A[/tex]
Proved.