Using trigonometric substitution, evaluate the following:

a$){\displaystyle \underset{\phantom{}}{\overset{\phantom{}}{}}}\frac{1}{3}cos5xsin2xdx$

b$){\displaystyle \underset{0}{\overset{3}{}}}\frac{1}{\sqrt[\phantom{2}]{(9-x^2)}}dx$

Determine:

a$){\displaystyle \underset{\phantom{}}{\overset{\phantom{}}{}}}\frac{5x-4}{2x^2+x-1}dx$

b$){\displaystyle \underset{\phantom{}}{\overset{\phantom{}}{}}}\frac{x^2+1}{x^2-3x+2}dx$