I.3.3.32 Definite Integrals

Condition: Find certain integrals. 1) \ (\ int_ {0}^{\ pi / 2} \ frac {d x} {3+ \ cos x} \); 2) \ (\ int_ {0}^{1} (2 x+1) e^{x+2} d x \); 3) \ (\ int_ {0}^{1} \ frac {d x} {e^{x} +2} \).