No, it is true of all pentagons.
Yes providing that they are regular 5 sided pentagons otherwise no if they are irregular pentagons
regular polygon mean equal sides, equal angles irregular polygon mean it is not equal :)
Pentagons do not have to be regular. Elongating one side will skew two angles and make them non congruent with the other three, creating an irregular polygon.
Yes. It doesn't matter how regular or irregular the sides are. "Five sides" means 540 degrees of interior angles.
A regular and an irregular octagon both have 8 interior angles
Yes, the sum of the interior angles will be 540 deg.
It depends on how they are classified. They can have 1 to 4 acute angles, they can have 1 to 4 right angles, they can have 1 to 5 obtuse angles. The individual values of the angles will generate different pentagons. They can be regular or irregular. They can be convex or concave.
Yes. All hexagons have interior angles totalling 720 degrees, whether they are regular or irregular. The proof of this is fairly easy.
Yes. In the regular polygon, the angles are all equal parts of the 1,080 . In the irregular one, there are bigger and smaller interior angles, but they still add up to the same total.