3)P{0<X<4,0<Y<5} 20 10J0x2(16+x2)(25+23cxdy 20c41 x2J016+x o25+y 4 arct 4 201 +0).1 5 arct+O 4 5 5 1- 4 ZT 4 16(3) P{0<X<4,0<Y<5} 16 1 4 1 4 1 0 5 5 5 1 0 4 4 4 20 1 25 1 16 20 1 (16 )(25 ) 20 2 5 0 2 4 0 2 2 5 0 4 0 2 2 2  =            =        +      =  + +  + = + + =            arctg arctg dy y dx x dxdy x y