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Question: Answered & Verified by Expert
2cos45°+cos56°+cos58°-cos66°2cos28°cos29°sin33°=
MathematicsTrigonometric EquationsJEE Main
Options:
  • A 2
  • B 22
  • C 22
  • D 42
Solution:
2559 Upvotes Verified Answer
The correct answer is: 22

Let

A=2cos45°+cos56°+cos58°-cos66°2cos28°cos29°sin33°

A=1-cos66°+cos56°+cos58°2cos28°cos29°sin90-57°

cos45°=12

A=1-1+2sin233°+2cos57°cos1°2cos28°cos29°sin90-57°

cosC+cosD=2cosC+D2cosC-D2cos2A=1-2sin2A

A=2cos257°+2cos57°cos1°2cos28°cos29°cos57°

A=2cos57°+cos1°cos28°cos29°

A=22cos57°+cos1°2cos28°cos29°

A=22cos57°+cos1°cos57°+cos1°

2cosAcosB=cosA+B+cosA-B

A=22

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