Quantitative Aptitude Ques 1202
Question: Find $ \frac{\tan 18{}^\circ }{\cot 72{}^\circ }-\frac{\cot 72{}^\circ }{\tan 18{}^\circ } $
Options:
A) $ 2 $
B) $ 1 $
C) $ 0 $
D) $ \sqrt{2} $
Show Answer
Answer:
Correct Answer: C
Solution:
- $ \frac{\tan 18{}^\circ }{\cot 72{}^\circ }-\frac{\cot 72{}^\circ }{\tan 18{}^\circ }=\frac{\tan (90{}^\circ -72{}^\circ )}{\cot 72{}^\circ }-\frac{\cot (90{}^\circ -18{}^\circ )}{\tan 18{}^\circ } $
$ =\frac{\cot 72{}^\circ }{\cot 72{}^\circ }-\frac{\tan 18{}^\circ }{\tan 18{}^\circ } $ $ [\because \tan (90{}^\circ -\theta )=\cot \theta ,cot(90{}^\circ -\theta )=tan\theta ] $
$ =1-1=0 $