Find the measure of one interior angle of a decagon?

Use the formula "total degrees= 180x(n-2), where n= number of sides of the figure. So, 8x180=1440 degrees, divided by 10 angles=144.

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The final part of the above answer is only true if all the angles of the decagon are equal. But there is no justification for assuming that the angles are all equal. In fact, they can have any value in the range (0, 360) degrees with the only restriction being that they add up to 1440 degrees.