Answer:D and E are correect
Step-by-step explanation:
Answer:

I inserted an image of the equation.
Step-by-step explanation:
Hope this helps!
Your answer is c, an obtuse triangle because if the two side lengths are the same length along with a longer side, it become obtuse
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Answer:
The regular polygon that she should use is an equilateral triangle
Step-by-step explanation:
The parameters given are;
Interior angles = 0.5 × Exterior angles
Exterior angles of a regular polygon = 360/n
Sum of interior angles of a regular polygon = (n - 2) × 180
Where n = the number of sides
Therefore, the sum of exterior angles of a regular polygon = 360°
Hence we have;
(n - 2) × 180 = 360/2 = 180
n - 2 = 180/180 = 1
n = 1 + 2 = 3 which is a three sided regular polygon or an equilateral triangle
Therefore, the regular polygon that she should use is an equilateral triangle