Two legs of a right triangle are each 70 cm. If one leg grows at the rate of 5cm/min and the oth
shrinks at the rate of 5 cm/min.
A)how fast is the hypotenuse of the triangle changing 2 minutes later?

Respuesta :

The rate of change of the hypotenuse after 2 minutes is 0.505 cm/min

Let L be the length of one leg and D be the length of  the other leg of the right triangle and y its hypotenuse

Since it is a right angled triangle, we have that, using Pythagoras' theorem

y² = L² + D²

Since the length of sides are the same, L = D = 70 cm.

So, y² = L² + D²

y² = 70² + 70²

y² = 2(70²)

y = 70√2

y = 98.99 cm

Also, one side increases at a rate of 5 cm/min and the other side decreases at a rate of 5 cm/min.

The increase in length of one side after 2 min is 5cm/min × 2 min = 10 cm.

So, it new length is L' = 70 + 10 = 80 cm

The decrease in length of the other side after 2 min is -5cm/min × 2 min = -10 cm.

So, it new length is D' = 70 + (-10 cm) = 60 cm

So, the new hypotenuse length is y' = √(L'² + D'²)

= √(80² + 60²)

= √(6400 + 3600)

= √10000

= 100 cm

Now, the change in length of the hypotenuse side in 2 minutes is Δy = 100 cm - 98.99 cm = 1.01 cm

So, rate of change of the hypotenuse after 2 minutes is 1.01 cm/2 min = 0.505 cm/min

The rate of change of the hypotenuse after 2 minutes is 0.505 cm/min

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