Quantitative Aptitude Ques 1352
Question: Value of $ {{\sec }^{2}}\theta +\frac{{{\sin }^{2}}\theta -2{{\sin }^{4}}\theta }{2{{\cos }^{4}}\theta -{{\cos }^{2}}\theta } $ is
Options:
A) $ 1 $
B) $ 2 $
C) $ -1 $
D) $ 0 $
Show Answer
Answer:
Correct Answer: A
Solution:
- $ {{\sec }^{2}}\theta -\frac{{{\sin }^{2}}\theta -2{{\sin }^{4}}\theta }{2{{\cos }^{4}}\theta -{{\cos }^{2}}\theta } $
$ ={{\sec }^{2}}\theta =\frac{{{\sin }^{2}}\theta ,(1-2{{\sin }^{2}}\theta )}{{{\cos }^{2}}\theta ,(2{{\cos }^{2}}\theta -1)} $
$ ={{\sec }^{2}}\theta -\frac{{{\sin }^{2}}\theta \cdot \cos 2\theta }{{{\cos }^{2}}\theta \cdot \cos 2\theta } $
$ [\because \cos 2\theta =1-2{{\sin }^{2}}\theta =2{{\cos }^{2}}\theta -1] $
$ ={{\sec }^{2}}\theta -{{\tan }^{2}}\theta =1 $