Answer:
(1) As a simple definition, a triangle is a two-dimensional figure that has 3 sides (and 3 angles as well).
(2) A triangle as shown in attached picture has the area that is typical calculated by the multiplication of half of base and height.
A = (1/2) x Base x Height
Base can be a particular side of triangle
Height is the perpendicular line segment between the opposite vertex of selected base and that base.
Hope this helps!
:)