The 3rd angle is 80 degrees
The information was certainly known to Euclid.
The interior angles of any triangle (not traingle) always sum to 180 degrees. Whether or not it is equilateral (not eguilateral) is irrelevant.
The three angles inside every triangle, no matter what shape or size it is, always add up to 180 degrees.
The isosceles triangle will have a top angle of 66 degrees and two equal base angles of 57 degrees which all add up to 180 degrees.
All triangles have to be 180 degrees so an isoceles is 180 degrees
The angles of all triangles have a sum of 180 degrees.An isoceles triangle has at least 2 equal sides (if all three are equal, it is an equilateral triangle).
isoceles
An isoceles triangle has 2 sides of equal length
yes
No because a right angle is a measurement of 90 degrees.
Two
at most, 1 in any triangle
3. every triangle have three sides
85 degrees
An isoceles is a type of triangle with two sides of equal length. Like all triangles an isoceles triangle has three interior angles.
All the angles in ANY triangle [on a plane surface] add up to 180 degrees.