Question
If $\theta=\cot ^{-1} 7+\cot ^{-1} 8+\cot ^{-1} 18$, then $\cot \theta$ is equal to(a) 1(b) 15(c) 3(d) 33
Step 1
We can rewrite this using the property $\cot^{-1}x = \tan^{-1}\frac{1}{x}$, so we get \[\theta=\tan ^{-1} \frac{1}{7}+\tan ^{-1} \frac{1}{8}+\tan ^{-1} \frac{1}{18}\] Show more…
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