Quantitative Aptitude Ques 2016
Question: If $ \sin \theta \cos \theta =\frac{\sqrt{3}}{2}, $ then the value of $ {{\sin }^{4}}\theta +{{\cos }^{4}}\theta $ is
Options:
A) $ \frac{7}{8} $
B) $ \frac{5}{8} $
C) $ \frac{3}{8} $
D) $ \frac{1}{8} $
Show Answer
Answer:
Correct Answer: B
Solution:
- Given that, $ \sin \theta \cdot \cos \theta =\frac{\sqrt{3}}{4} $
(i)
Now, we have $ {{\sin }^{4}}\theta +{{\cos }^{4}}\theta $
$ ={{({{\sin }^{2}}\theta +{{\cos }^{2}}\theta )}^{2}}-2{{\sin }^{2}}\theta {{\cos }^{2}}\theta $
$ ={{(1)}^{2}}-2{{(\sin \theta \cos \theta )}^{2}} $
$ =1-2{{( \frac{\sqrt{3}}{4} )}^{2}}=1-2\cdot \frac{3}{16}=1-\frac{3}{8}=\frac{5}{8} $