If A = 60°, then what is the value of $(4 \, cos^3\, A - 3 cos \, A )$ ?
Answer & explanation
Correct answer: option 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