What's a radian? What is the unit circle? What are the Pythaafereum Identities?

Question

Please help!

*Pythagoreans.How many radians are in 360?

Answer 1

A radian is an angular measurement. A radian of arc has length equal to the radius of the circle. Since the circumference of a circle is 2*pi*r, there are 2*pi radians in a circle.

The unit circle is a circle with radius equal to 1 (in a coordinate system, so the units can be anything). It normally has its center at the origin.

The Pythagorean trigonometric identity states that sin^2(x) + cos^2(x) = 1, and it follows from the Pythagorean theorem. Two equivalent statements, 1 + tan^2(x) = sec^2(x) and 1 + cot^2(x) = csc^2(x), are also called Pythagorean identities.

Answer 2

radian is an angle subtended at the centre of the circle by an arc of this circle of length equal to its radius.