Limits and Continuity

1. Evaluate the following limit.  solution

(a)  \( \displaystyle{\lim_{(x,y)\to(1,-2)} \frac{xy}{x^2+y^2}} \)

 

(b)  \( \displaystyle{\lim_{(x,y)\to(0,\pi/4)}  x+\tan y - \sin (x-y) } \)

 

 

Show that each of the following limits doesn't exist.

2. \( \displaystyle{\lim_{(x,y)\to(0,0)} \frac{3x^2-y^2}{x^2+2y^2}} \)    solution

 

3. \( \displaystyle{\lim_{(x,y)\to(0,0)} \frac{2xy}{x^2+y^2}} \)   solution

 

4. \( \displaystyle{\lim_{(x,y)\to(0,0)} \frac{2xy^2}{x^2+y^4}} \)      solution

 

5. Evaluate the limit.   \( \displaystyle{\lim_{(x,y)\to(0,0)} \frac{5x^2y}{x^2+y^2}} \)   solution   (not in test 2)