Question

Cos6° cos24° cos72°=

Answer 1

=cos6.sin24cos72

=cos6.sin24.cos(90-18)

=1/2[2cos6.sin24}(sin18)

=1/2[ sin(6+24)-sin(6-24)]sin18

=1/2[sin30.sin18+sin18.sin18]

=1/2[1/2*(5^1/2-1)/2) + {(5^1/2-1)/2}^2]

After simplyfing we get,

=1/8

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Answer 2

Answer:

= cos6.sin24cos72 = cos6.sin24.cos(90 - 18) = 1/2[2cos6.sin24(sin18) = 1/2[ sin(6 + 24) - sin(6 - 24)]sin18 = 1/2[sin30.sin18 + sin18.sin18] = 1/2[1/2*(51/2 ...

Step-by-step explanation:

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