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When the area of a square is increasing four times as fast as the diagonals, what is the length of a side of the square

Sagot :

Answer:

Length of a side of a square = 2√2 units

Step-by-step explanation:

Let the length of a square is 'x' units.

Therefore, Area of the square A = (Side)²

                                                      = x² square units

And by Pythagoras theorem,

(Diagonal)²= (Side 1)² + (Side 2)²

                 = x² + x²

                 = 2x²

Diagonal 'p' = x√2 units

It is given in the question that area of the square is increasing four times as fast as the diagonals.

[tex]\frac{d(A)}{dt}=4(\frac{dp}{dt} )[/tex] -------(1)

[tex]\frac{d(A)}{dt}=\frac{d(x^2)}{dt}[/tex]

[tex]\frac{d(A)}{dt}=2x\frac{d(x)}{dt}[/tex]

Similarly, [tex]\frac{d(p)}{dt}=\frac{d(x\sqrt{2})}{dt}[/tex]

                      [tex]=\sqrt{2}\frac{dx}{dt}[/tex]

Now by placing the value of [tex]\frac{d(A)}{dt}[/tex] and [tex]\frac{d(p)}{dt}[/tex] in equation (1),

[tex]2x\frac{dx}{dt}=4\sqrt{2}\frac{dx}{dt}[/tex]

[tex](2x - 4\sqrt{2})\frac{dx}{dt}=0[/tex]

Since, [tex]\frac{dx}{dt}\neq 0[/tex]

[tex](2x - 4\sqrt{2})=0[/tex]

x = 2√2

Therefore, length of a side of the square is 2√2.

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