MCQ
$\tan3\text{A}-\tan2\text{A}-\tan\text{A}$ is equal to:
- A$\tan3\text{A}\tan2\text{A}\tan\text{A}$
- B$-\tan3\text{A}-\tan2\text{A}\tan\text{A}$
- C$\tan\text{A}\tan2\text{A}\tan2\text{A}\tan3\text{A}-\tan3\text{A}\tan\text{A}$
- DNon of these
Solution:.
$3\text{A}=2\text{A}+\text{A}$
$\Rightarrow\tan3\text{A}=\tan(2\text{A}+\text{A})$
$\Rightarrow\tan3\text{A}=\tan(2\text{A}+\text{A})=\frac{\tan2\text{A}+\tan\text{A}}{1-\tan2\text{A}\tan\text{A}}$
$\Rightarrow\tan3\text{A}-\tan3\text{A}\tan2\text{A}\tan\text{A}=\tan2\text{A}+\tan\text{A}$
$\Rightarrow\tan3\text{A}-\tan2\text{A}-\tan\text{A}=\tan3\text{A}\tan2\text{A}\tan\text{A}$
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The name of the conic represent by the equation x2 + y2 - 2y + 20x + 10 = 0 is: