A rectangle is constructed with its base on the x-axis and two of its vertices on the parabola yx. What are the dimensions of the rectangle with the maximum area? What is that area?

The answer is below

Step-by-step explanation:

The question is not complete, the complete question is:

A rectangle is constructed with its base on the x-axis and two of its vertices on the parabola y 81-x², what are the dimensions of the rectangle with the maximum area? what is the area?

Solution:

Given the parabola:

y = 81 - x²

Let the points (a,0) and (-a, 0) be points on the axis, this points touch the parabola at (a, 81 - a²) and (-a, 81 - a²).

Points (a,0), (-a, 0), (a, 81 - a²), (-a, 81 - a²) form the rectangle.

The length of rectangle = distance between (a,0) and (-a, 0) or between (a, 81 - a²) and (-a, 81 - a²) = 2a

The breadth of rectangle = distance between (a,0) and (a, 81 - a²) or between (-a, 0) and (-a, 81 - a²) = 81 - a²

Area of rectangle (A) = length × breadth = 2a × (81 - a²) = 162a - 2a³

A = 162a - 2a³

The maximum area is at dA / da = 0

dA / da = 162 - 8a² = 0

162 - 6a² = 0

6a² = 162

a² = 27

a = 5.2 units

Length = 2a = 2(5.2) =  10.4 units

Breadth = 81 - a² = 81 - 5.2² = 54 unit

Area = length × breadth = 54 × 10.4 = 561 unit²

b. an equilateral triangle inscribed in a circle

step-by-step explanation:

we are given the figure of two circles having a triangle inside.

now, we know that,

"when a figure is lying inside an another figure, then the outside figure is known as circumscribed figure and the figure lying inside is referred to as the inscribed figure".

as we see that, the circles are containing the triangle completely.

thus, the circles are the circumscribed figures and the triangle is the inscribed figure.

hence, we get, 'an equilateral triangle is inscribed in a circle'.

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