A solid lies between planes perpendicular to the x-axis at x = -2 and x = 2. The cross-sections perpendicular to the x-axis b
etween these planes are squares whose bases run from the semicircle y = -√(4 - x²) to the semicircle y = √(4 - x²).
Find the volume of the solid.
Find the volume of the solid.
1 answer:
Answer:
V = 128π/3 vu
Step-by-step explanation:
we have that: f(x)₁ = √(4 - x²); f(x)₂ = -√(4 - x²)
knowing that the volume of a solid is V=πR²h, where R² (f(x)₁-f(x)₂) and h=dx, then
dV=π(√(4 - x²)+√(4 - x²))²dx; =π(2√(4 - x²))²dx ⇒
dV= 4π(4-x²)dx , Integrating in both sides
∫dv=4π∫(4-x²)dx , we take ∫(4-x²)dx and we solve
4∫dx-∫x²dx = 4x-(x³/3) evaluated -2≤x≤2 or too 2 (0≤x≤2) , also
∫dv=8π∫(4-x²)dx evaluated 0≤x≤2
V=8π(4x-(x³/3)) = 8π(4.2-(2³/3)) = 8π(8-(8/3)) =(8π/3)(24-8) ⇒
V = 128π/3 vu
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One of the symmetries of this cross is right here. (Picture 2) It splits the cross into <em>two identical halves</em>, one a mirror image of the other. Most importantly, <em>the angles on each side of the line are identical</em>. We can draw this same mirror into our problem, too (picture 3). This symmetry tells us that those two unknown angles are exactly the same - <em>equal</em>. So, if angle MNJ is 5x+2 and angle LNK is 3(x+14), we now know that
5x + 2 = 3(x + 14), or, getting our algebra sorted:
5x + 2 = 3x + 42
2x = 40
x = 20
Now that we know x, we can find MNJ - which, because X's are symmetric, is exactly the same angle as LNK. Crunching the numbers, we find
m∠MNJ = m∠LNK = 5(20) + 2 = 100 + 2 = 102°.
Side note: the technical term for pairs of angles like MNJ and LNK is vertical angles. What we've shown here is, because of the symmetry of intersecting lines, vertical angles are always equal.
Answer:
Step-by-step explanation:
Given
Required
Since the events are mutually exclusive, then:
So, we have:
Take LCM