二、课后练习答案：（不抄题目，没有课本的人可以到网上去下一本）
2.6.
（1）自己运行一下就知道了
（2）这个程序的作用是已知三角形三边求三角形的面积
（3）转载
//#include <stdio.h>
#include <iostream.h>
#include <iomanip.h>
#include <math.h>

void main()
{
  float a,b,c,s,area;
  //printf("please input 3 sides of one triangle:\n");
  cout <<"please input 3 sides of one triangle:\n";
  //scanf("%f,%f,%f",&a,&b,&c);  //输入时以逗号作为数据间隔
  cin >>a >>b >>c;   //输入时以空格作为数据间隔

  s=(a+b+c)/2;
  area=sqrt(s*(s-a)*(s-b)*(s-c));

  //printf("a=%7.2f,b=%7.2f,c=%7.2f\n",a,b,c);
  cout <<setiosflags(ios::fixed) <<setprecision(2)
       <<"a=" <<setw(7) <<a
       <<",b=" <<setw(7) <<b
       <<",c=" <<setw(7) <<c <<endl;
  //printf("area of triangle is %10.5f",area);
  cout <<"area of triangle is " <<setw(10)
       <<setprecision(5) <<area <<endl;
}
（4）转载
#include <iostream.h>
#include <iomanip.h>
#include <math.h>

float area(float a, float b, float c); //函数声明

void main()
{
  float a,b,c;
  cout <<"please input 3 sides of one triangle:\n";
  cin >>a >>b >>c;   //输入时以空格作为数据间隔

  float result = area(a,b,c);          //函数调用

  cout <<setiosflags(ios::fixed) <<setprecision(2)
       <<"a=" <<setw(7) <<a
       <<",b=" <<setw(7) <<b
       <<",c=" <<setw(7) <<c <<endl;
  cout <<"area of triangle is " <<setw(10)
       <<setprecision(5) <<result <<endl;
}

float area(float a, float b, float c)  //函数定义
{
  float s=(a+b+c)/2;
  return sqrt(s*(s-a)*(s-b)*(s-c));
}


2.7
说明：
（1）.这个程序主要是在演示函数调用的调用过程
（2）.最后的语句getche();的作用是输入一个字符，当然你可以把这个输入的字符赋值给你所定义的某个字符
结果是：
In main():
Enter two numbers:
5 6

Calling add():
In add(),received 5 and 6
and return 11

Back in main():
c was set to 11

Exiting...
aPress any key to continue



2.8
#include<iostream>
using namespace std;
const double PI=3.14159;
double Calvolume(double,double);//函数声明
void main()
{
    double radius,height,volume;
    cout<<"Enter The radius&height of column:\n";
    cin>>radius>>height;

    volume=Calvolume(radius,height);//函数调用

    cout<<"The volume of colunm is "<<volume<<endl;
}

double Calvolume(double radius,double height)//函数定义
{
    return PI*radius*radius*height;
}


That is OK! Thank you!

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