下列程序对加号进行了重载,划线部分的语句是______。 include include class

下列程序对加号进行了重载，划线部分的语句是______。

include＜iostream.h＞

include＜math.h＞

class Triangle

{

int x,y,z;

double area;

public:

Triangle(int i,int j,int k)

{

double s;

x=i;y=j;z=k;

s=(x+y+z)/2.0;

area=sqrt(s*(s-x)*(s-y)*(s-z));

}

void disparea( )

{

cout＜＜"Area="＜＜area＜＜endl;

}

friend double operator+(Triangle tl,Triangle t2)

{

______

}

};

void main( )

{

Triangle tl(3,4,5),t2(5,12,13);

double s;

cout＜＜"tl:";t1. disparea( );

cout＜＜"t2:";t2. disparea( );

s=t1+t2:

cout＜＜"总面积：="＜＜s＜＜endl;

}