General Certificate of Secondary Education (GCSE) Maths Practice Exam

The value of sin 90° is 1. This result is derived from the unit circle, which is a fundamental concept in trigonometry. In the unit circle, angles are measured from the positive x-axis, and the sine of an angle represents the y-coordinate of the point on the circle corresponding to that angle.

At 90°, the point on the unit circle is at the coordinates (0, 1). Since the sine function corresponds to the y-coordinate, sin 90° equals 1. This aligns with the geometric interpretation of sine, where the maximum value of sine occurs at 90°, providing a clear understanding of why sin 90° is defined as 1.

The other options reflect values of the sine function at different angles: 0 corresponds to angles like 0° and 180°, 0.5 corresponds to 30°, and -1 corresponds to 270°. Therefore, the only value that correctly represents sin 90° is 1.