The triangle has uniform surface mass density of. The method that I've been taught involves some basic integration and substitution of dm for (Density X dA). And then substituting dA with one expression in terms of dy, and another in terms of dx. I don't really like the method I was taught... 'feels' inconsistent. I don't like having to look at the graph to determine an expression for dA... I keep thinking that if the problem gets tougher, like with some complex graph, then I'm screwed. What I was wondering however, is if we could use double integration to solve it? I haven't really learnt double integration, but I've sorta used it for moments of areas. So for example, maybe we could make the substitution dm = (density) dx dy? Then do some fancy math? It just seems more logical. I hope I'm making sense. Any advise?