Question: If $ (\cos \theta +\sec \theta )=2, $ then $ ({{\cos }^{2}}\theta +{{\sec }^{2}}\theta ) $ is equal to
Options:
A) $ \frac{1}{2} $
B) 2
C) 4
D) $ \frac{1}{4} $
Show Answer
Answer:
Correct Answer: B
Solution:
- $ \cos \theta +\sec \theta =2 $
$ {{(\cos \theta +\sec \theta )}^{2}}={{(2)}^{2}} $ [squaring on both sides]
$ {{\cos }^{2}}\theta +{{\sec }^{2}}\theta +2\cos \theta \times \sec \theta =4 $
$ \Rightarrow $ $ {{\cos }^{2}}\theta +{{\sec }^{2}}\theta +2=4 $
$ \Rightarrow $ $ {{\cos }^{2}}\theta +{{\sec }^{2}}\theta =4-2 $
$ \Rightarrow $ $ {{\cos }^{2}}\theta +{{\sec }^{2}}\theta =2 $