How do you identify the value of cos 5π/6?

Question

nathan917 · Answer

Draw a full circle, cut with two right angle lines.

what is the angular size of a full circle?
how big is 1/4 circle?
what does the fraction of a circle have to do with Pi?

You nead to understand how an angle is measure in size.

The idea of a "Radian" angle is a little strange at first.

What is the length of a straight line? you measure it compared to a standard length of "1"

You cannot measure a curve like a circle because it has on straight pieces.

We Define the length of the circumference of a full circle to be PI times Diameter or Pi times 2 Radius.

the circular angle is the length of the curve of a part of a circle in ratio ( divided by) the R. so the angle of a full circle is 2 Pi in units of "Radians", the angular measure of part of a circle is the curve length / R = fraction of the whole circle x 2 Pi Radians

I did not understand radian measure at first either.

360 degrees is just an arbitrary but useful fraction of a full circle that goes back to ancient times.