hello. The problem is : A metallic horizontal disk of radius R has been charged on its top surface with a total charge Q such that its surface charge density is "non uniform" and governed by the expression σ=q|cosθ|*r where r and θ are the polar coordinates measured from the center O of the disk. Determine in terms of Q and R the value of q. I tried to solve it using double integral but it didn't work. σ=dq/ds then dq=q|cosθ|*r*rdrdθ then ∫dq/q=0∫R 0∫2∏|cosθ|dθr2dr. If any body can help thanks.