Question : If $\tan A = n\tan B$ and $\sin A=m \sin B$, then the value of $\cos^{2}A$ is:
Option 1: $\frac{m^{2}-1}{n^{2}+1}$
Option 2: $\frac{m^{2}+1}{n^{2}-1}$
Option 3: $\frac{m^{2}+1}{n^{2}+1}$
Option 4: $\frac{m^{2}-1}{n^{2}-1}$
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Correct Answer: $\frac{m^{2}-1}{n^{2}-1}$
Solution : $\sin A = m\sin B$--------------(i) $\tan A = n\tan B$ $\frac{\sin A}{\cos A}$ = $n\frac{\sin B}{\cos B}$------------------(ii) Substituting $\sin B$ from equation (i), ⇒ $\cos B$ = $\frac{n}{m}$$\cos A$----------(iii) Squaring both sides of equation (i), ⇒ $\sin^{2} A$ = $m^{2}\sin^{2}B$ ⇒ 1–$\cos^{2} A$ = $m^{2}(1–\cos^{2} B)$ Substituting equation (iii), 1–$\cos^{2} A$ = $m^{2}(1–\frac{n^{2}}{m^{2}}$$\cos^{2} A)$ $\cos^{2} A$ = $\frac{m^{2}-1}{n^{2}-1}$ Hence, the correct answer is $\frac{m^{2}-1}{n^{2}-1}$.
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Question : If $0°<A<90°$, the value of $\frac{\tan A\ -\ \sec A\ -\ 1}{\tan A\ +\ \sec A\ +\ 1}$ is:
Option 1: $\frac{\sin A-1}{\cos A}$
Option 2: $\frac{1-\sin A}{\cos A}$
Option 3: $\frac{1-\cos A}{\sin A}$
Option 4: $\frac{\sin A+1}{\cos A}$
Question : If $\frac{\cos\alpha}{\cos\beta}= m$ and $\frac{\cos\alpha}{\sin\beta}= n$, then the value of $(m^{2}+n^{2})\cos^{2}\beta$ is:
Option 1: n2
Option 2: m2
Option 3: mn
Option 4: 1
Question : In $\triangle ABC$, right angled at B, if $\tan A=\frac{1}{2}$, then the value of $\frac{\sin A(\cos C+\cos A)}{\cos C(\sin C-\sin A)}$ is:
Option 1: $2$
Option 2: $1$
Option 3: $3$
Option 4: $2\sqrt5$
Question : If $\tan \theta=\frac{4}{3}$, then the value of $\frac{3\sin \theta+ 2\cos \theta}{3\sin \theta – 2 \cos \theta}$ is:
Option 1: $\frac{1}{2}$
Option 2: $1\frac{1}{2}$
Option 4: $–3$
Question : If $\tan A=\frac{3}{8}$, then the value of $\frac{3 \sin A+2 \cos A}{3 \sin A-2 \cos A}$ is:
Option 1: $-\frac{13}{25}$
Option 2: $-\frac{25}{7}$
Option 3: $\frac{25}{8}$
Option 4: $\frac{13}{21}$
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