Study of triangles and trigonometric functions including sine, cosine, and tangent.
Angles can be measured in degrees (°) or radians. There are 360° in a circle, but only \(2\pi\) radians.
\[ 360^\circ = 2\pi \text{ radians} \] \[ 1 \text{ radian} = \frac{180^\circ}{\pi} \]
The unit circle is a circle with a radius of 1 centered at the origin of a coordinate plane. Each point on the circle corresponds to an angle, and its coordinates \((x, y)\) are \((\cos \theta, \sin \theta)\).
It helps us understand trigonometric functions for all angles, not just those in right triangles.
Converting 90° to radians: \(90^\circ = \frac{\pi}{2}\) radians.
On the unit circle, the coordinates at 180° are (-1, 0).
The unit circle links angles, radians, and trigonometric functions in a visual way.