Prove the following identities, where the angles involved are acute angles for which the expressions are defined.
$\sqrt{\frac{1+\sin A }{1-\sin A }}=\sec A +\tan A$
$\sqrt{\frac{1+\sin A }{1-\sin A }}=\sec A +\tan A$
$L.H.S.=\sqrt{\frac{1+\sin A }{1-\sin A }}$
$=\sqrt{\frac{(1+\sin A )(1+\sin A )}{(1-\sin A )(1+\sin A )}}$
$=\frac{(1+\sin A )}{\sqrt{1-\sin ^{2} A }}=\frac{1+\sin A }{\sqrt{\cos ^{2} A }}$
$=\frac{1+\sin A }{\cos A } \quad=\sec A +\tan A$
$= R . H.S.$
State whether the following are true or false. Justify your answer.
The value of $\cos \theta$ increases as $\theta$ increases
Evaluate the following:
$\sin 60^{\circ} \cos 30^{\circ}+\sin 30^{\circ} \cos 60^{\circ}$
$9 \sec ^{2} A-9 \tan ^{2} A=..........$
If $\sin 3 A =\cos \left( A -26^{\circ}\right),$ where $3 A$ is an acute angle, find the value of $A= . . . . ^{\circ}$.
Consider $\triangle ACB$, right-angled at $C$, in which $AB =29$ units, $BC =21$ units and $\angle ABC =\theta$ (see $Fig.$). Determine the values of
$(i)$ $\cos ^{2} \theta+\sin ^{2} \theta$
$(ii)$ $\cos ^{2} \theta-\sin ^{2} \theta$