Question

if 7A = π, prove that cosA cos2A cos3A = 1/8

Answer 1

HEY MATE HERE IS YOUR ANSWER

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given: 7A = 180.........(1)
LHS of the given equation is:
cosAcos2Acos3A=cosAcos2Acos(180−4A) [since 3A=180−4A]=cosAcos2A*[−cos4A]=−cosAcos2Acos4A=−12sinA(2sinAcosA)cos2Acos4A [multiplying and dividing by 2sinA=−12sinA*sin2Acos2Acos4A=−14sinA(2sin2Acos2A)cos4A=−14sinAsin4Acos4A=−18sinA(2sin4Aco4A)
=−18sinA*sin8A=−18sinA*sin(7A+A)=−18sinA*sin(180+A)=−18sinA*(−sinA)=18
= RHS

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Answer 2

Answer:

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Step-by-step explanation:

this is your answer

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