15
1/2*(152-3*15) = 90
Chat with our AI personalities
The shape you are describing is a rhombus. A rhombus has two pairs of parallel sides, with opposite sides being equal in length. The diagonals of a rhombus are also equal in length, but they do not intersect at 90 degrees; instead, they intersect at a 90-degree angle.
A square has perpendicular diagonals. They are all the same angle (90 degrees). All sides are the same length. To find area of a square, use the formula A=4s. (Area=4xthe lenghth of the sides.)
Number of diagonals in a polygon with n sides is n*(n-3)/2 A pentadecagon has 15 sides, so n = 15 Number of diags = 15*12/2 = 90
There are 90 diagonals in a 15-sided polygon.
1/2*15*(15-3) = 90 diagonals.