www.quickanddirtytips.com/education/math/why-does-a-triangle-have-180-degrees

And our little drawing shows that the exterior angle in question is equal to the sum of the other two angles in the triangle. In other words, the other two angles in the triangle (the ones that add up to form the exterior angle) must combine with the angle in the bottom right corner to make a 180 0 angle.

www.mathsisfun.com/proof180deg.html

The top line (that touches the top of the triangle) is running parallel to the base of the triangle. So: angles A are the same ; angles B are the same ; And you can easily see that A + C + B does a complete rotation from one side of the straight line to the other, or 180°

www.khanacademy.org/.../v/proof-sum-of-measures-of-angles-in-a-triangle-are-180

I've drawn an arbitrary triangle right over here. And I've labeled the measures of the interior angles. The measure of this angle is x. This one's y. This one is z. And what I want to prove is that the sum of the measures of the interior angles of a triangle, that x plus y plus z is equal to 180 degrees.

www.answers.com/Q/Do_all_triangles_equals_180

In an equilateral trianger, each angle is 60 degrees. In all triangles, including equilateral triangles, all 3 angles add up to 180 degrees. (the above assumes Euclidean - flat - space.

www.answers.com/Q/Why_does_a_triangle_equal_to_180_degrees

No, because the angles of a triangle have to total 180 degrees and if there are three angles in a triangle, 90 * 3 cannot equal 180. To have three equal sides, the angles must equal 60 degrees 60 ...

en.wikipedia.org/wiki/Sum_of_angles_of_a_triangle

In several geometries, a triangle has three vertices and three sides, where three angles of a triangle are formed at each vertex by a pair of adjacent sides. In a Euclidean space, the sum of measures of these three angles of any triangle is invariably equal to the straight angle, also expressed as 180 °, π radians, two right angles, or a half ...

www.answers.com/Q/Why_Do_the_angles_of_all_triangles_equal_a_180_degrees

No because a triangles inner angles must equal a whole 180 degrees and an equilateral has to have all equal interior angles and 75+75+75 does not equal 180 Load More. Trending Questions.

mathcentral.uregina.ca/QQ/database/QQ.09.06/becky1.html

Why does a triangle always equal 180 degrees? We know that all the angles add up to 180 degrees but cant find a valid reason for it. Hi Becky, Suppose that you had a right angle triangle. Note that if you take it and another copy of it (moved around a bit) the two triangles together can be placed to make a rectangle. ...

www.answers.com/Q/What_angle_is_equal_to_180_degrees

A pair of supplementary angles add up to 180 degrees. Therefore, the supplement of any angle x is equal to 180 - x degrees. For example, the supplement of a 130 degree angle is equal to 180 - 130 ...