



 
Hi Carla, I added four lines to your diagram to complete the regular pentagon ABCDE. Since ABCDE is a regular pentagon the measure of the angle ABC is π  2π/5 = 3π/5 radians. Triangle ABC is isosceles and hence the measure of the angle BCA is (π  3π/5)/2 = π/5 radians. The measure of the angle BCD is 3π/5 radians so the measure of the angle ACD is 3π/5  π/5 = 2π/5 radians. Triangle CDA is also isosceles and hence the measure of angle DAC is π  2 × 2π/5 = π/5 radians. Is this enough to get you started? Harley  


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