Show that 8 cos,^3 20° -6 cos 20º = 1
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Step-by-step explanation:
First step is take 2common = 2(4cos^3 20° -3 cos 20°). Now, 4cos^3 theta - 3cos theta = cos(3theta) , here theta is 20°, Hence, the value of 2(4cos^3 theta -3cos theta) = 2(cos(3×20) ) = 2(cos60°) = 2( 1/2) =1. since cos60°=1/2, Hence it is verified. Hope this helps you.
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