MCQ
The expression
$ \cos ^2(A-B)+\cos ^2 B-2 \cos (A-B) \cos A \cos B $ is
  • A
    dependent on B
  • B
    dependent on A - B
  • dependent on A
  • D
    independent of A and B

Answer

Correct option: C.
dependent on A
(C)
$\cos ^2(A-B)+\cos ^2 B-2 \cos (A-B) \cos A \cos B$
$=\cos ^2(A- B )+\cos ^2 B$$-\cos ( A - B )\{\cos ( A - B )+\cos ( A + B )\}$
$=\cos ^2 B-\cos ( A - B ) \cos ( A + B )$
$=\cos ^2 B-\left(\cos ^2 A-\sin ^2 B\right)$
$=1-\cos ^2 A$
Hence, it depends on A.

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