The exact value of sin 30 degrees is 1/2.
This can be understood through the properties of a right triangle. In a 30-60-90 triangle, the side lengths are in the ratio 1 : √3 : 2. The sine of an angle is defined as the ratio of the length of the opposite side to the length of the hypotenuse. For a 30 degree angle, the side opposite this angle is 1 (the shorter leg), and the hypotenuse is 2. Therefore, sin 30° = opposite/hypotenuse = 1/2.