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If A = 60°, then what is the value of $(4 \, cos^3\, A - 3 cos \, A )$ ? |
-1 $-\frac{\sqrt{3}}{2}$ $\frac{\sqrt{3}}{2}$ 1 |
-1 |
4cos³A - 3cosA Put A = 60º = 4cos³ 60º - 3cos 60º = 4 ×( \(\frac{1}{2}\) )³ - 3 ×( \(\frac{1}{2}\) ) = 4 ×( \(\frac{1}{8}\) ) - 3 ×( \(\frac{1}{2}\) ) = ( \(\frac{1}{2}\) ) - ( \(\frac{3}{2}\) ) = -1 |
