North has 0 degree and right angle has 90 degree although both are in same position

Question

Before reading trigonometry I guessed that if a line is pointing to north then it has 0 degrees and increases clockwise. But now I see right angle has 90 degree though that is in the same position as north?

Is it because angles for navigation are different than the angles we read in trigonometry? or I have to understand in a different way?

Answer 1

Yes. Different structures. Trig/Unit Circle starts with zero at "East" and increases in a counterclockwise direction. Bearings and directions use vertical-up as zero degrees.

Answer 2

Angle is a property not of one line, but of two intersecting lines. In your question the second line is implicit but different in both cases (going north for navigation, going to the right for trigonometry.) This is by convention and has no real meaning except it makes it easier for you to talk about angles since you need to mention only one line...

To make things slightly more complicated, the orientation is also different. Angles in trigonometry are positive in counter-clockwise direction, while in navigation positive angles go from the north in clockwise direction.