The following integrals calculate areas of regions in the xy-plane. Say what shape each integral gives the area of. Be specific; for example, if the shape is a rectangle, give the base and height of the rectangle. Include a sketch of the region, showing the variable of integration, an arbitrary slice, and any other relevant quantities.

a. ∫ 3xdx
b. ∫ √15-y^2dy
c. ∫ √81- x^2 dx
d. ∫ (5- y/7)dy

Respuesta :

Answer:

a. [tex]\frac{3}{2}[/tex]

b. [tex]\frac{15\pi }{4}[/tex]

c. [tex]\frac{81\pi }{2}[/tex]

d. [tex]\frac{7}{2}[/tex]

Step-by-step explanation:

P.S - The exact question is -

a. [tex]\int\limits^1_0 {3x} \, dx[/tex]

y = 3x

Shape of the given integral = A Triangle

Area of Triangle = [tex]\int\limits^1_0 {3x} \, dx[/tex] = [tex]\frac{1}{2}[/tex]×1×3 = [tex]\frac{3}{2}[/tex]

The graph of integral is as follows :

b.[tex]\int\limits^\15 _0 {\sqrt{15 - y^{2} } } \, dy[/tex]

x = [tex]\sqrt{15 - y^{2} }[/tex]

⇒x² = 15 - y²

⇒x² + y² = 15

⇒x² + y² = (√15)²

Shape of the integral = Quarter circle of radius √15

Area of Quarter circle = [tex]\int\limits^\15 _0 {\sqrt{15 - y^{2} } } \, dy[/tex] = [tex]\frac{1}{4}[/tex]×[tex]\pi[/tex]×r² = [tex]\frac{1}{4}[/tex]×[tex]\pi[/tex]×(√15)² = [tex]\frac{15\pi }{4}[/tex]

The graph of the following integral is as follows :

c.[tex]\int\limits^9_-9 {\sqrt{81 - x^{2} } } \, dx[/tex]

y = [tex]\sqrt{81 - x^{2} }[/tex]

⇒y² = 81 - x²

⇒y² + x² = 81

⇒y² + x² = 9²

Shape of the integral = Semi circle of radius 9

Area of semi circle = [tex]\int\limits^9_-9 {\sqrt{81 - x^{2} } } \, dx[/tex] = [tex]\frac{1}{2}[/tex]×[tex]\pi[/tex]×r² =  [tex]\frac{1}{2}[/tex]×[tex]\pi[/tex]×9² = [tex]\frac{81\pi }{2}[/tex]

The graph of the following integral is as follows :

d. [tex]\int\limits^7_0 {5 - \frac{y}{7} } \, dy[/tex]

x = 5 - [tex]\frac{y}{7}[/tex]

⇒[tex]\frac{y}{7}[/tex] = 5 - x

⇒y = 35 - 7x

At y = 0 , x = 5

At y = 7 , x = 4

Shape of the integral = A triangle

Area of Triangle = [tex]\frac{1}{2}[/tex]×(5-4)×7 =  [tex]\frac{1}{2}[/tex]×(1)×7 = [tex]\frac{7}{2}[/tex]

The graph of the integral is as follows :

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