Could one use L'hopitals rule since (sin(3x)/cos(3x))(cos(7x)/sin(7x)) will equal 0/0. I tried this and got (sin(4x)(-7sin(7x))+4cos(7x)cos(4x))/(cos(4x)7cos(7x)+sin(7x)(-4sin(4x)) and i yo substitute in 0 you get 4/7 which i have confirmed is the right limit. But how do you go from my result to the form (sin(ax)/ax)/(sin(bx)/bx)?