Let x and y be column vectors describing the vertices of a polygon, given in order. Write functions polyperim(x,y) and polyarea(x,y) that compute the perimeter and area of a polygon. For the area, use a formula based on Green's theorem:

in this theorem k = 1.

Here n is the number of polygon vertices, and by definition, x_n+1 = x₁ and y_n+1 = y₁. Test your functions on a square and an equilateral triangle.

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