The base of a triangle is shrinking at a rate of 11 cm/s and the height of the triangle is increasing at a rate of 11 cm/s. Find the rate at which the area of the triangle changes when the height is 10cm and the base is 8cm.

Answer :

Answer:

the rate of changes  of the area of the triangle

[tex]\frac{dA}{dt} = -11 cm^2 /sec[/tex]

Step-by-step explanation:

Explanation :-

The area of triangle( A) = [tex]\frac{1}{2} base X height[/tex]    ..........(1)

Let 'b' be the base and 'l' be the length of the triangle

The base of a triangle is shrinking( means decreasing) at a rate of 11 cm/s

that is [tex]\frac{db}{dt} = -11cm/sec[/tex]

The height of a triangle is increasing at a rate of 11 cm/s

that is [tex]\frac{dh}{dt} = 11cm/sec[/tex]

Given h= 10cm and b = 8cm

The rate of change of triangle

applying uv formula  [tex]\frac{d(uv)}{dx} = u( \frac{dv}{dx}) + v(\frac{du}{dx} )[/tex]

Differentiating equation (1) with respective to 't'

[tex]\frac{dA}{dt} =\frac{1}{2} ( b(\frac{dh}{dt} )+h ( \frac{db}{dt}))[/tex]

substitute all values in above equation, we get

h= 10cm , b = 8cm , [tex]\frac{db}{dt} = -11cm/sec[/tex] and [tex]\frac{dh}{dt} = 11cm/sec[/tex]

 [tex]\frac{dA}{dt} = 10 (-11) + 8(11 )[/tex]

After simplification , we get

[tex]\frac{dA}{dt} =\frac{1}{2} (-110 +88) = -11 cm^2 /sec[/tex]

Answer:

The area of the triangle is decreasing at a rate 11 square centimeter per second            

Step-by-step explanation:`  

We are given the following in the question:

[tex]\dfrac{db}{dt} = -11\text{ cm per sec}\\\\\dfrac{dh}{dt} = 11\text{ cm per sec}[/tex]

Instant base = 8 cm

Instant height = 10 cm

Area of triangle =

[tex]A = \dfrac{1}{2}\times b \times h[/tex]

where b is the base of the triangle and h is the height of the triangle.

Rate of change of area =

[tex]\dfrac{dA}{at} = \dfrac{1}{2}(b\dfrac{dh}{dt} + h\dfrac{db}{dt})[/tex]

Putting values, we get,

[tex]\dfrac{dA}{dt} = \dfrac{1}{2}(8(11) + (10)(-11))\\\\\dfrac{dA}{dt}=-11[/tex]

Thus, the area of the triangle is decreasing at a rate 11 square centimeter per second

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