Question 82

Find the value of $$\cos 120^\circ \cos 240^\circ \cos 180^\circ \cos 60^\circ$$.

Solution

$$\cos 120^\circ \cos 240^\circ \cos 180^\circ \cos 60^\circ$$

$$\cos 120^\circ$$=$$\frac{-1}{2}$$

$$\cos 240^\circ$$=$$\frac{-1}{2}$$

$$\cos 180^\circ$$ = -1

$$\cos 60^\circ$$=$$\frac{1}{2}$$

put the value in equation

$$\cos 120^\circ \cos 240^\circ \cos 180^\circ \cos 60^\circ$$

we get

$$\frac{-1}{8}$$

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