718 Square and Triangles | Centroid of Composite Area

Problem 718
Locate the centroid of the shaded area shown in Fig. P-718.
 

Trapezoidal area with isosceles triangle subtracted from the bottom

 

Solution 718

 

Comments

for x2, why is it (1/2)(12) and not (2/3)(12)?

Based on the formula for centroids, solving for x in an equilateral triangle will only equate to zero if it is placed along the origin. Therefore, we are just going to figure out the distance of the triangle from the origin.