คำตอบ - Trigonometry

The period of trigonometric functions is 360 degrees.

$$\sin \left(630°\right)=\sin \left(630-360°\right)$$

Subtracting one integer from another.

$$\sin \left(630-360°\right)=\sin \left(270°\right)$$

Reflecting the number with respect to 360 degrees.

$$\sin \left(270°\right)=\sin \left(360-90°\right)$$

The period of trigonometric functions is 360 degrees.

$$\sin \left(360-90°\right)=\sin \left(360-90-360°\right)$$

Removing or simplifying the same numbers on the top and bottom of a fraction.

$$\sin \left(360-90-360°\right)=\sin \left(-90°\right)$$

Computing the sine of a negative angle.

$$\sin \left(-90°\right)=-\sin \left(90°\right)$$

Computing the sine of 90 degrees.

$$-\sin \left(90°\right)=-1$$