Volumes of cylinders and cones

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Volumes of cylinders and cones
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Zusammenfassung der Ressource

Frage Antworten
How do we find the volume of a cylinder? π x r^2 x h
What is the formula involving the summation for volume of a cone? π x lim(δ->0) x (b)Σ(a) x y^2 x δx
What do a and b represent in this formula? The limits of the x-value
What does δx represent in this formula? The thickness of the rectangles we are using to estimate the volume of the cone
Why should δx be as low as possible? It will give a more accurate volume
Ways to improve our volume estimation are: Increasing number of rectangles and increasing number of cylinders
Image to visualize it:
This imagine represents: Rectangles along x-axis rotation by 360 degrees (revolution)
As δx approaches 0, the sum becomes an.... Integral
Another way to find the volume of a cone rotated by 360 degrees in the x-axis is by using the formula..... π x b∫a (y^2) dx
We can also find the volume of a cone rotated 360 degrees in the y-axis by.... π x b∫a (x^2) dx
1. Region bounded between x^2 +5 between x=0 and x=4 and the x-axis is rotated 360 degrees about x-axis. Find the volume to 3sf π x 4∫0 (x^2+5)^2 dx 4∫0 (x^2+5)^2 dx = 518.133 518.133 x π = 1627.76 3sf = 1630
2. Region bounded between x^2 +5 between y=6 and y=10 and the y-axis is rotated 360 degrees about the y-axis. Find the volume to 3sf Rearrange y=x^2 +5 for x^2=y-5 so we can use formula π x b∫a (x^2) dx So 10∫6 (y-5)^2 dx = 12 π x 12 = 37.699 3sf = 37.7
3. Region bounded by y=3x^2 +1 between x=0 and x=2 and the y-axis is rotated by 360 degrees about the y-axis. Find the volume to 3sf Find y boundaries: 3(0)^2 + 1 = 1 3(2)^2+1 = 13 y=3x^2 +1 rearranged = x^2 = (y-1)/3 Now: π x 13∫1 (y-1)/3 dx = 75.4
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