Solve sin(-30^circ)*cos(-60^circ)

$$\sin ( - 30 ^ { \circ } ) \cdot \cos ( - 60 ^ { \circ } )$$

Evaluate

$$-\frac{1}{4}=-0.25$$

Solution Steps

Use \sin(x)\cos(y)=\frac{1}{2}\left(\sin(x-y)+\sin(x+y)\right) to obtain the result.

$$\frac{1}{2}\left(\sin(-30+60)+\sin(-30-60)\right)$$

Subtract -60 from -30. Add -60 to -30.

$$\frac{1}{2}\left(\sin(30)+\sin(-90)\right)$$

Get the value of \sin(30) from trigonometric values table.

$$\frac{1}{2}\left(\frac{1}{2}+\sin(-90)\right)$$

Use the property \sin(-x)=-\sin(x).

$$\frac{1}{2}\left(\frac{1}{2}-\sin(90)\right)$$

Get the value of \sin(90) from trigonometric values table.

$$\frac{1}{2}\left(\frac{1}{2}-1\right)$$

Do the calculations.

$$-\frac{1}{4}$$