Question

Why is the sum of all the angles of a triangle 180 degree?

Answer 1

In a Euclidean space, the sum of measures of these three angles of anytriangle is invariably equal to the straight angle, also expressed as 180°, π radians, two right angles, or a half-turn. It was unknown for a long time whether other geometries exist, where this sum is different.



The angle sum of a Triangle is 180° - lesson with proof & varied exercises. Above, you probably made a guess that the sum of the angles in a triangle is 180°. ... The three angles A', B', and C' form together a straight angle (they are along the line l). So, their angle sum is 180°.