Question 165480
Please solve this question. 
Q 1. Write down an equation or equations for each of the following. 
a. A plane parallel to xy-plane at a distance of 4 units from origin on negative z-axis. 
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z = -4.  For all values of x and y, z is 4.
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b. A curve produced due to the intersection of a circular cylinder and yz-plane. Center of this circular cylinder is x-axis (that is, cylinder is around x-axis) and its radius is one. 
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The intersection is a circle about the origin.
{{{y^2 + z^2 = 1}}}

c. A curve produced due to the intersection of a sphere, center at origin and radius 3, and xy-plane. 
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This is also a circle about the origin.  Any plane intersecting a sphere will be a circle.
{{{x^2 + y^2 = 3^2}}}
{{{x^2 + y^2 = 9}}}