8cos^3 π/9 - 6cosπ/9
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Prove that; 8cos3(π9)−6cos(π9)=1
My Attempt,
L.H.S=8cos3(π9)−6cos(π9)
=2cos(π9)[4cos2(π9)−3]
=2cos(π9)[2+2cos(2π9)−3]
=2cos(π9)[2cos(2π9)−1]
.
My Attempt,
L.H.S=8cos3(π9)−6cos(π9)
=2cos(π9)[4cos2(π9)−3]
=2cos(π9)[2+2cos(2π9)−3]
=2cos(π9)[2cos(2π9)−1]
.
Manishhhhh:
haan but define me
the step plz
2nd step
okay thanks
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