The unit circle definition of sine, cosine, & tangent
A unit circle intends a circle with a radius of 1 unit.
It is an excellent idea to understand and communicate regarding lengths and trigonometric functions.
In the fig. where the x-axis and y-axis cross, so we can calculate the neat arrangement here.
Sine, Cosine and Tangent
The trig functions & right triangle trig ratios
As we know the radius of the circle is 1, then we can immediately calculate sine, cosine, and tangent.
What happens when we put the angle, θ, is 0°?
cos 0° = 1,
sin 0° = 0
and tan 0° = 0
What happens when we put the angle, θ, is 90°?
cos 90° = 0,
sin 90° = 1
and tan 90° = undefined