五角形內角的總和是多少?

=(n-2)*180
= (5-2)*180
=540

=180(n-2) (angle sum of polygon)
=180(5-2)
=180*3
=540(度)

You can use the formula 180(n-2) where n = number of vertices of a polygon.

In that case, a pentagon has 5 vertices and hence the sum of its internal angles = 180(5-2) = 540 degrees.

You may interpret the formula as the number of non-overlapping triangles of a polygon that can be formed by joining the same vertex and every adjacent side. For a polygon with n vertices, there are n sides and there are 2 sides (i.e. the side with the fixed vertex as an endpoint) that cannot be formed a triangle with the fixed vertex. Then, (n-2) such triangles can be constructed. As we know the sum of all internal angles of a triangle is 180 degrees, and hence the formula follows.

你可以利用以下公式幫助你計算不同形狀的內角和：
(n-2)*180度

由於今次是要計算五角形的內角 總和，
所以(5-2)*180度=540度

五角形內角的總和是:
(5-2)*180
=3*180
=540(度)

using formula:(n-2)*180

2007-02-26 13:06:18 補充：
by myself knowledge