Triangles are one type of polygon
No.
180 degrees
It can be but need not be.
half of base times altitude.
trianle have no faces, because it is 2D figure.
This is the formula to find the hypotenuse of a right angle trianle
180 degrees
They are both polygons.They have a different number of sides/angles.
An equilateral triangle has 3 equal interior angles each measureing 60 degrees
Trianle Tri is Latin for three, angle is of obscure derivation.
it seems to me that the only polygon of your description is a square
A triangle has three sides and three angles. Right angled triangles are triangles in which the measure of one angle equals 90 degrees