MHB Calculating Radius of Circular Section from Sphere and Plane Intersection

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To find the radius of the circular section formed by the intersection of the sphere defined by x^2 + y^2 + z^2 = 49 and the plane 2x + 3y - z - 5√14 = 0, one approach is to calculate the distance from the sphere's center to the plane. This distance can be determined using the formula d = |Ax0 + By0 + Cz0 + D| / √(A^2 + B^2 + C^2). Once the distance d is found, the radius r of the circular section can be derived using the right triangle formed by the sphere's radius and the distance to the plane. This method simplifies the problem without needing to substitute z back into the sphere's equation. The final radius of the circular section can then be calculated effectively.
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Find the radius of the circular section of the sphere of the sphere x^2 + y^2 + z^2 = 49 by the plane 2x+3y-z-5 \sqrt{14}= 0
 
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Suppose you solve the equation of the plane for $z$, and then substitute for $z$ into the equation of the sphere...what do you get?
 
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I think it is easier to find the distance $d$ from the center of the sphere to the plane (recall the the distance from $(x_0,y_0,z_0)$ to $Ax+By+Cz+D=0$ is $\dfrac{Ax_0+By_y+Cz_0+D}{\sqrt{A^2+B^2+C^2}}$) and then find the radius $r$ of the required circular section from the right triangle.
 

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Here is a little puzzle from the book 100 Geometric Games by Pierre Berloquin. The side of a small square is one meter long and the side of a larger square one and a half meters long. One vertex of the large square is at the center of the small square. The side of the large square cuts two sides of the small square into one- third parts and two-thirds parts. What is the area where the squares overlap?

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