State whether the following are true or false. Justify your answer.
$(i)$ $\cos A$ is the abbreviation used for the cosecant of angle $A$
$(ii)$ cot $A$ is the product of cot and $A$.
$(iii)$ $\sin \theta=\frac{4}{3}$ for some angle $\theta$.
$(iii)$ Abbreviation used for cosecant of angle $A$ is cosec $A$. And $\cos A$ is the abbreviation used for cosine of angle $A$
Hence, the given statement is false.
$(iv)$ cot $A$ is not the product of cot and $A$. It is the cotangent of $\angle A$.
Hence, the given statement is false.
$(v)$ $\sin \theta=\frac{4}{3}$
We know that in a right-angled triangle,
$\sin \theta=\frac{\text { Side opposite to } \angle \theta}{\text { Hypotenuse }}$
In a right-angled triangle, hypotenuse is always greater than the remaining two sides. Therefore, such value of $\sin \theta$ is not possible.
Hence, the given statement is false
Show that:
$(i)$ $\tan 48^{\circ} \tan 23^{\circ} \tan 42^{\circ} \tan 67^{\circ}=1$
$(ii)$ $\cos 38^{\circ} \cos 52^{\circ}-\sin 38^{\circ} \sin 52^{\circ}=0$
$\frac{1+\tan ^{2} A}{1+\cot ^{2} A}=........$
If $\tan 2 A=\cot \left(A-18^{\circ}\right),$ where $2 A$ is an acute angle, find the value of $A .$ (in $^{\circ}$)
$9 \sec ^{2} A-9 \tan ^{2} A=..........$
$\sin 2 A=2 \sin A$ is true when $A=$