## Thomas' Calculus 13th Edition

a )$\sqrt{y^2+z^2}$; b) $\sqrt{x^2+z^2}$ c) $\sqrt{x^2+y^2}$
a) The distance between two points is: $\sqrt{(x-x_0)^2+(y-y_0)^2+(z-z_0)^2}$ Need to find the distance from point $P(x,y,z)$ to the x-axis or $(x,0,0)$. $\sqrt{(x-x)^2+(y-0)^2+(z-0)^2}=\sqrt{y^2+z^2}$ b) The distance between two points is: $\sqrt{(x-x_0)^2+(y-y_0)^2+(z-z_0)^2}$ Need to find the distance from point $P(x,y,z)$ to the y-axis or, $(0,y,0)$. $\sqrt{(x-0)^2+(y-y)^2+(z-0)^2}=\sqrt{x^2+z^2}$ c) The distance between two points is: $\sqrt{(x-x_0)^2+(y-y_0)^2+(z-z_0)^2}$ Need to find the distance from point $P(x,y,z)$ to the z-axis or $(0,0,z)$. $\sqrt{(x-0)^2+(y-0)^2+(z-z)^2}=\sqrt{x^2+y^2}$