Question 732254
a seismograph located 10 miles due north of a recording station detects a n earthquake with epicenter 15 miles away.

Write an equation that could be used to describe possible locations of the epicenter.
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Using the location of the seismograph as the origin (0,0,0),
the earthquake's location is on a sphere {{{x^2 + y^2 + z^2 = 15^2}}}, 
where z is the depth and is negative.