Math, asked by umesh156, 8 months ago

what is the answer for the given question​

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Answered by nehareddy7
1

Answer:

1/8

Step-by-step explanation:

cos pi/7 × cos 2pi/7 × cos 3pi/7

"now , we now sin2a = 2sinacosa"

multiply and divide by 2sin pi/7

1/2sin pi/7 { 2sin pi/7 cos pi/7 × cos 2pi/7 × cos 3pi/7 }

1/2sin pi/7 { sin 2pi/7 cos 2pi/7 × cos 3pi/7 }

"now , multiply and divide by 2"

1/2×2sin pi/7 { 2sin 2pi/7 cos 2pi/7 × cos 3pi/7 }

1/4sin pi/7 { sin 4pi/7 × cos 3pi/7 }

"as we now sin ( pi - theta ) = sin theta "

'sin ( pi - 4pi/7 ) = sin 3pi/7' , substitute this value,,,

1/4sin pi/7 { sin 3pi/7 cos 3pi/7 }

" again multiply and divide by 2 "

1/2×4sin pi/7 { 2sin 3pi/7 cos 3pi/7 }

1/8sin pi/7 { sin 6pi/7 }

" we can write sin 6pi/7 as sin ( pi - pi/7 ) and the value of sin ( pi - pi/7 ) = sin pi/7 ,,, substitute it "

NOW,,

sin pi/7/8sin pi/7

= 1/8

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