9 Four students were asked to write an expression that is
1 answer:
You might be interested in
This is usually used as a proof that triangles have 180°. Look at the attached figures. If you cut off angle A, angle B and angle C and rotate them so that their vertices touch, you form a half-circle out of them (or a straight line). We know that half a circle is 1/2 of 360° or 180; therefore all 3 angles in a triangle must add up to 180°.
