Similar figures: side lengths and angle measures
The triangles are similar. Find the value of x. 


Write proportions using corresponding parts. Then solve to find the missing mearure.


Definition of similar polygon 
x(8)=4(4)


Cross product 
8x=16


Simplify 


Divide each side by 8 
x=2 

Simplify 
If these two figures are similar, what is the measure of the missing angle? 


Since the shapes are similar and corresponding angles in similar shapes have the same measure, the measure of the missing angle is 131º.