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Mathematics 8 Online
boredfr:

I need help .-. Calc https://padlet-uploads.storage.googleapis.com/1140267424/aeb3c96a1f1771b861f8e4382ef5baef/Screenshot_2021_05_03_at_7_51_39_PM.png

boredfr:

@AZ

surjithayer:

find the eq. of two lines on left of y-axis and right of y-axis.also find the eq. of circle with center (5,3) and radius=3 take f(x)=y break interval from -2 to 0,0 to 2 and 2 to 5 integrate inthese intervals ,then add you get integration -2 to 5 integration from -6 to 5=integration from -6 to -2 plus integration from -2 to 5 from this you can find your reqd.result for (a)

surjithayer:

\[\int\limits_{-6}^{5}f(x)dx=\int\limits_{-6 }^{-2}f(x)dx+\int\limits_{-2}^{-1}f(x)dx+\int\limits_{-1}^{0}(-f(x))dx\]\[+\int\limits_{0}^{0.5}[-f(x)]dx+\int\limits_{0.5}^{2}f(x)dx+\int\limits_{2}^{5}f(x) dx\]

surjithayer:

\[\int\limits_{-2}^{-1 }f(x)dx=\frac{ base \times height }{ 2 }=\frac{ 1\times1 }{ 2 }=\frac{ 1 }{ 2 }\]

surjithayer:

@surjithayer wrote:
\[\int\limits_{-1}^{0}(-f(x) )dx=\frac{ base \times \times height }{ 2 }=\frac{ 1\times1 }{ 2}=\frac{ 1 }{ 2 }\]

surjithayer:

\[\int\limits_{0}^{0.5}[-f(x) ]dx=\frac{ base \times height }{ 2 }=\frac{ 0.5 \times 1 }{ 2 }=\frac{ 1 }{ 4 }\]

surjithayer:

\[\int\limits_{0.5}^{2}f(x) dx=\frac{ base \times height }{ 2 }=\frac{ 1.5 \times 3 }{ 2 }=\frac{ 9 }{ 4 }\]

surjithayer:

\[\int\limits_{2}^{5}f(x) dx=3^2-\frac{ \pi \times 3^2}{ 4 }=9-\frac{ 9 \pi }{ 4 }\] area under the circular arc= area of square-area of quarter circle (r=3)

surjithayer:

i have solved without integration. If you want i can solve with integration also. Then you have to find the eq. of two lines and circle then evaluate one by one.

surjithayer:

now you substitute for all and find the reqd. result.

surjithayer:

for b \[\int\limits_{3}^{5}(2f'(x)+4)dx=2\int\limits_{3}^{5}f'(x) dx+4\int\limits_{3}^{5}dx=2f(x)[3 \rightarrow 5]+4(x)[3 \rightarrow 5]\] eq. of circle is \[(x-5)^2+(y-3)^2=3^2\] \[y-3=\sqrt{9-(x-5)^2}\] when x=3 \[y-3=\sqrt{9-4}\] \[y=3+\sqrt{5}\] when x=5 \[y-3=\sqrt{9-0},y=3+3=6\] so f(x) from 3 to 5 is \[6-(3+\sqrt{5})=3-\sqrt{5}\] assume y= f(x)

surjithayer:

\[\int\limits_{3}^{5}(2 f'(x)+4)dx=2(3-\sqrt{5})+4(5-3)=6-2\sqrt{5}+8=14-2\sqrt{5}\]

boredfr:

I don't get it .-.

surjithayer:

|dw:1620178074951:dw| let y=f(x) be the curve. Then \[\int\limits_{a}^{b}ydx=\int\limits_{a}^{b}f(x) dx\] It gives the area between ABDC. it is the area under the curve and x-axis between x=a to x=b

surjithayer:

if the curve remains above x-axis then reqd. area\[=\int\limits_{a}^{b }ydx\] if it is below x-axis then area\[=\int\limits_{a}^{b}(-y)dx=\int\limits_{a}^{b}(-f(x))dx\]

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