On the complex plane, a regular polygon formed by connecting each consecutive point that is a solution to the equation is centered at the origin and has a vertex at Let A be the minimum possible number of sides found on this polygon, and let B be area of the polygon with A sides. Find the value of A B
You may use a calculator to evaluate the area of the polygon | |
is the imaginary unit |
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The point z = ( 2 3 + 2 i ) is on a regular polygon centered at the origin. This tells us that the polygon is inscribed in a circle of radius 1 centered at the origin, and z = ( 2 3 + 2 i ) is a point on the circle in the complex plane. Thus, x = 2 3 = cos 3 0 ∘ and y = 2 1 i = i sin 3 0 ∘ . . ∴ The angle between the points 1 , 0 and ( 2 3 + 2 i ) is 3 0 ∘ . So each point on the polygon is separated by 3 0 ∘ of arc on the unit circle. Thus, the polygon has ( 3 0 ∘ 3 6 0 ∘ ) = 1 2 sides. Therefore, the minimum possible number of sides the polygon has is 1 2 . . So A = 1 2 . The area of the dodecadgon ( 1 2 sides) is: A ∘ = r 2 1 2 sin ( 9 0 ∘ − 1 2 1 8 0 ∘ ) ∙ cos ( 9 0 ∘ − 1 2 1 8 0 ∘ ) . A ∘ = 1 2 sin ( 7 5 ∘ ) cos ( 7 5 ∘ ) = 4 1 2 = 3 . So A = 1 2 and B = 3 . ∴ A + B = 1 5 .