How angles formed?

Answer 1

Angles are formed by measuring a line from the centre of a circle to the edge of the circle marked in degrees, minutes and seconds. A protractor and ruler are commonly used to measure and draw angles.

A complete circle is 360 degrees.
A half circle is 180 degrees.
A quarter circle is 90 degrees.

A right-angle triangle has one corner with an angle of 90 degrees. The two other angles are both 45 degrees. 90 + 45 + 45 = 180 degrees (half a circle).
The right-angle triangle is actually half of a square. If two such triangles were to be joined together to form a square, all angles will add up to 360 degrees.
90 + 45 + 45 =180 x 2 = 360 degrees.