Question

Earthquakes release seismic waves that occur in concentric circles from the epicenter of the earthquake. Suppose a seismograph station determines the epicenter of an earthquake is located 9 kilometers from the station. If the epicenter is located at the origin, write the equation for the circular wave that passes through the station.
A. x2 + y2 = 81
B. x2 + y2 = 9
C. (x - 9)2 + (y - 9)2 = 0
D. (x + 9)2 + (y + 9)2 = 0

Answer 1

Equation of a circle with center (a, b) and radius r is
\[(x-a)^2+(y-b)^2=r^2\]
here (a, b)= (0, 0) and radius =9 km so
\[ (x-0)^2+(y-0)^2=9^2\]
or
\[x^2+y^2=81\]

Answer 2

Thank You !

Answer 3

Welcome :)