Tính các tích phân sau:
a/ $\int_{0}^{\frac{\pi }{4}}\frac{tanx}{cos^{2}x}dx$
b/ $\int_{0}^{\frac{\pi }{4}}tanx.dx$
c/ $\int_{0}^{\frac{\pi }{4}}tan^{3}x.dx$
d/ $\int_{0}^{1}t^{3}\left ( 1+t^{4} \right )^{3}dt$
e/ $\int_{0}^{1}\frac{5x}{\left ( x^{2}+4 \right )^{2}}dx$
f/ $\int_{0}^{\sqrt{3}}\frac{4x}{\sqrt{x^{2}+1}}dx$
g/ $\int_{0}^{\frac{\pi }{6}}\left ( 1-cos3x \right )sin3x.dx$