Question

If angel B = 30°, find the value of 3cosB - 4 cos³ B.​

Answer 1

Answer:

1

Cos30=$\frac{1}{2}$

(3 × $\frac{1}{2}$)-(4 × $\frac{1}{8}$)=$\frac{3}{2}$-$\frac{1}{2}$=1

Answer 2

3 cos30 - 4 $cos^{3}$30

=  -cos3*30

= -cos90

=0