I need someone to help me!! i have been given a center point of (3,-1,-2) of a sphere and i need to get an equation for when it is tangent to the a) the yz plane b) y=7. i know i need to use the distance formuala to attain the radius, but i am majorly confusing myself in what coordinate to pick. Do i just use (0,0,0) as tangent point to the plane for a)?? please help!