7. Вычислите ∫ (π/4)π/3 (dx / cos² 3x)
π3 π/3 ∫ dx/cos2(3x)=1/3·tg3x| =1/3·((tg(3·π/3)–tg(3·π/4))=1/3·(0+1)=1/3 π/4 π/4