Trigonometric EquationHard
Question
If cos-1 x - cos-1
= α then 4x2 - 4xy cos α + y2 is equal to
= α then 4x2 - 4xy cos α + y2 is equal to Options
A.2 sin 2α
B.4
C.4 sin2 α
D.- 4 sin2 α
Solution
cos-1 x - cos-1 = α
cos-1
= α
cos-1
= α
⇒ 4 - y2 - 4x2 + x2y2 = 4 cos2α + x2y2 - 4xy cosα
⇒ 4x2 + y2 - 4xy cosα = 4 sin2α
= αcos-1
= αcos-1
= α⇒ 4 - y2 - 4x2 + x2y2 = 4 cos2α + x2y2 - 4xy cosα
⇒ 4x2 + y2 - 4xy cosα = 4 sin2α
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