Hey everyone, I can't figure this problem out:

Find the constants a and b that will make the following function continuous everywhere.

f(x)=

Thanks in advance!

- $\displaystyle a cosx$ if x<0
- sin$\displaystyle \left(\frac{pi}{2}x+3)$ if 0<=x<=2
- $\displaystyle x^2-x+b$ if x>2