Problem:
In the adjoining figure, CDE is an equilateral triangle and ABCD and DEFG are squares. The measure of ∠GDA is
Answer Choices:
A. 90∘
B. 105∘
C. 120∘
D. 135∘
E. 150∘
Solution:
The measures of angles ∠ADC,∠CDE and ∠EDG are 90∘,60∘ and 90∘, respectively. Hence the measure of ∠GDA is
360∘−(90∘+60∘+90∘)=120∘.