The perimeter of the two rectangles A and B is equal, and the total area is 165 square centimeters. The length width ratio of rectangle A is 5:3, and that of rectangle B is 7:5, What is the area of a rectangle?

The perimeter of the two rectangles A and B is equal, and the total area is 165 square centimeters. The length width ratio of rectangle A is 5:3, and that of rectangle B is 7:5, What is the area of a rectangle?

Let rectangular a be a square centimeter in length and b square centimeter in width. Rectangular B be m square centimeter in length and n square centimeter in width ∵ A / b = 5 / 3, M / N = 7 / 5 ∵ a = b * 5 / 3, B = a * 3 / 5, M = n * 7 / 5, n = m * 5 / 7 ∵ a + B = m + n ∵ b * 5 / 3 + B = n * 7 / 5 + N

How to calculate the area of regular polygon?

Nsqrt (3) a ^ 2 / 4A is the length of the side, n is the number of sides, sqrt (3) is the root sign 3. This paper proves that if the area of a positive n-polygon is s, then s = (1 / 2) NR ^ 2 * sin α = NR ^ 2tan (α / 2), where n -- the number of sides, R -- the radius of the circumscribed circle of the triangle, R -- the radius of the inscribed circle of the triangle, α -- the angle of the center of the circle opposite to one side (in degrees)

Area formula of regular polygon
Is there a good formula to express the area of regular polygon?
If there is
To prove the method!

Yes. Let the area of a regular n-shape be s, then s = (1 / 2) NR ^ 2 * sin α = NR ^ 2tan (α / 2), where n -- the number of sides, R -- the radius of the circumscribed circle of the triangle, R -- the radius of the inscribed circle of the triangle, and α -- the angle of the center of the circle opposite one side (in degrees) are proved very simple