PLEASE HELP ME!!
For the circle centered at the origin with radius 4 and equation x^2+y^2=16, find dx/dt at the first quadrant point where x=2 if dy/dt=-3 at that instant.

Respuesta :

Answer:

dx/dt = 12

Step-by-step explanation:

Given the  equation of a circle expressed as:

x²+y² = 16

Differentiate the expression with respect to x

2x dx/dt + 2y dy/dt = 0

Given

x = 2

dy/dt = 3

Required

dx/dt

Substitute the given parameters into the resulting differential equation

2x dx/dt + 2y dy/dt = 0

2 dx/dt + 2(4) (-3) = 0

y = 4 since the radius is 3,

2 dx/dt - 24 = 0

2 dx/dt = 24

dx/dt = 24/2

dx/dt = 12

Using implicit differentiation, it is found that:

[tex]\frac{dx}{dt} = 4 + 3\sqrt{3}[/tex]

The equation of the circle is:

[tex]x^2 + y^2 = 16[/tex]

We are given x = 2, then:

[tex]2^2 + y^2 = 16[/tex]

[tex]y^2 = 12[/tex]

[tex]y = \pm \sqrt{12}[/tex]

First quadrant, thus, positive:

[tex]y = \sqrt{12}[/tex]

[tex]y = 2\sqrt{3}[/tex]

Applying implicit differentiation, we have that:

[tex]2x\frac{dx}{dt} + 2y\frac{dy}{dt} = 16[/tex]

We are given that [tex]frac{dy}{dt} = -3[/tex], then:

[tex]2(2)\frac{dx}{dt} - 12\sqrt{3} = 16[/tex]

[tex]4\frac{dx}{dt} = 16 + 12\sqrt{3}[/tex]

[tex]\frac{dx}{dt} = \frac{16 + 12\sqrt{3}}{4}[/tex]

[tex]\frac{dx}{dt} = 4 + 3\sqrt{3}[/tex]

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