A square and an equilateral triangle are joined to form the polygon shown what is the sum of the interior angles of the polygon 240 degrees 360 degrees 420 degrees 540 degrees

540°

Step-by-step explanation:

An equilateral triangle has 3 interior angles of 60°

A square has 4 interior angles of 90°.

When the images are joined, two vertices of each figures are joined together, such that these angles will have now a measure of:

60° + 90° = 150°

Then this figure has:

one angle of 60°

two angles of 150°

and two angles of 90°

(the image below illustrates this situation)

The sum of the interior angles is:

S = 60° + 2*150° + 2*90° = 540°

step-by-step explanation:

ca = ec

cpctc makes it so that corresponding parts of the triangle you proved to be equal are equal, the other options aren't part of the part of the triangles you proved to be equal.