Question: What is the value of $ \sin A+\cos A\tan A+\cos A\sin A\cot A? $ [CDS 2012]
Options:
A) $ {{\sin }^{2}}A+\cos A $
B) $ {{\sin }^{2}}A+{{\tan }^{2}}A $
C) $ {{\sin }^{2}}A+{{\cot }^{2}}A $
D) $ cose{c^{2}}A-{{\cot }^{2}}A $
Show Answer
Answer:
Correct Answer: D
Solution:
- $ \sin A\cos A\tan A+\cos A\sin A\cot A $
$ =\sin A\cos A\frac{\sin A}{\cos A}+\cos A\sin A\frac{\cos A}{\sin A} $
$ ={{\sin }^{2}}A+{{\cos }^{2}}A=1 $ $ [\because {{\sin }^{2}}\theta +{{\cos }^{2}}\theta =1] $
$ =cose{c^{2}}A-{{\cot }^{2}}A $ $ [\because 1+{{\cot }^{2}}\theta =cose{c^{2}}\theta ] $