Trigonometric Equations Question 234
Question: In $ \Delta ABC $ , $ c\cos (A-\alpha )+a\cos (C+\alpha )= $
Options:
A) $ a\cos \alpha $
B) $ b\cos \alpha $
C) $ c\cos \alpha $
D) $ 2b\cos \alpha $
Show Answer
Answer:
Correct Answer: B
Solution:
- $ c\cos (A-\alpha )+a\cos (C+\alpha ) $ $ =c(\cos A\cos \alpha +\sin A\sin \alpha ) $ $ +a(\cos C\cos \alpha -\sin C\sin \alpha ) $ $ =\cos \alpha (c\cos A+a\cos C)+c,\sin A\sin \alpha -a\sin C\sin \alpha $
Þ $ b\cos \alpha +kac\sin \alpha -kac\sin \alpha =b\cos \alpha $ .
BETA
