If A+B+C=pi , prove that cos 2A +cos ...

If `A+B+C=pi `, prove that
`cos 2A +cos 2B +cos 2C=-1-4cos A cos Bcos C.`

A

`-1+4 sin A cos B sin C`

B

`-1+4 sin A sin B cos C`

C

`-1-4 cos A cos B cos C`

D

`1+4 sin A sin B sin C`

Verified by Experts

The correct Answer is:

C

FACTORIZATION FORMULAE
TARGET PUBLICATION|Exercise COMETITIVE THINKING|34 Videos
FACTORIZATION FORMULAE
TARGET PUBLICATION|Exercise EVALUATION TEST|8 Videos
FACTORIZATION FORMULAE
TARGET PUBLICATION|Exercise EVALUATION TEST|8 Videos
CIRCLE AND CONICS
TARGET PUBLICATION|Exercise EVALUATION TEST|28 Videos
PROBABILITY
TARGET PUBLICATION|Exercise EVALUATION TEST|8 Videos

Similar Questions

Explore conceptually related problems

If A+B+C = pi , prove that : cos2A +cos2B +cos2C =-1-4cosAcosBcosC .

In a /_ABC prove that cos2A+cos2B+cos2C=-1-4cos A cos B cos C

If A+B+C=pi, prove that cos 2A-cos 2B-cos 2C=-1+4cos A sinBsinC

Theorem 2:cos2A+cos2B+cos2C=-1-4cos A cos B cos C

If A+B+C = pi prove that cos 4A + cos 4B + cos 4C = -1 + 4 cos 2A cos 2B cos 2C

If A+B+C = pi , prove that : cos2A-cos2B -cos2C = -1+4cosAsinBsinC

If A+B+C=180, prove that cos^(2)A+cos^(2)B+cos^(2)C=1-2cos A cos B cos C

If A+B+C=pi , prove that : cos2A+cos2B-cos2C=1-4sinA sinB cosC

If A + B + C = pi , prove that cos A cosec B cosec C + cos B cosec C cosec A + cos C cosec A cosec B = 2 .

If A+B+C+pi , prove that cos4A+cos4B+cos4C=-1+4cos2Acos2Bcos 2C.