Trigonometric Equations Question 115
Question: If the sides of a $ \Delta $ be $ (x^{2}+x+1),,(2x+1) $ and $ (x^{2}-1), $ then the greatest angle is
[EAMCET 1987; Kerala (Engg.) 2001]
Options:
A) $ 105^{o} $
B) $ 120^{o} $
C) $ 135^{o} $
D) None
Show Answer
Answer:
Correct Answer: B
Solution:
- Sides are $ (x^{2}+x+1),,(2x+1),,(x^{2}-1) $ . The greatest side subtends the greatest angle. Hence $ x^{2}+x+1 $ is the greatest side. Now $ \cos \theta =\frac{{{(2x+1)}^{2}}+{{(x^{2}-1)}^{2}}-{{(x^{2}+x+1)}^{2}}}{2(2x+1)(x^{2}-1)} $
$ \Rightarrow $ $ \theta =120^{o} $ .
BETA
