This double integral is a nightmare! The integral of cos(x/(y+1)) is impossible to integrate with respect to y but we will use the most important trick in Calculus 3: Changing the Order of Integration! We will graph the region, then switch the order of dydx, work out the inner integral, then use integration by parts (DI method) to finish this hard double integral! #Calculus3 #DoubleIntegrals #CalculusTricks