矩阵法和梯形法求定积分

(1)矩阵法求定积分，积分函数f(x)=1+Exp(x)

Program main

implicit none
real :: a,b,x                  ！a,b分别是下限和上限
integer :: n,counter    ！n是分成的份数
real :: step,fx               ！step是步长，由上限，下限，份数决定
real :: area,Integral   ！area是小矩阵元面积，Integral  是所有矩阵元之和
Integral=0.0

write(*,*) "a=,b="
read(*,*)a,b
write(*,*) "n="
read(*,*) n
step=(b-a)/real(n)

do counter=1,n-1,1
x=a+counter*step
fx=1+EXP(x)
area=fx*step
Integral=Integral+area
end do
write(*,*)"Definite Integral:",Integral
stop

End Program main

（2）梯形法求定积分（与矩形法没有本质区别）

Program main

implicit none
real :: a,b,x1,x2
integer :: n,counter
real :: step
real :: fx1,fx2,area,Integeral
Integeral=0.0

write(*,*) "Input a:"
read(*,*) a
write(*,*) "Input b:"
read(*,*) b
write(*,*) "Input n:"
read(*,*) n

step=(b-a)/real(n)

do counter=1,n-1,1
x1=a+counter*step
x2=x1+step
fx1=1+EXP(x1)
fx2=1+EXP(x2)
area=0.5*(fx1+fx2)*step
Integeral=Integeral+area
end do

write(*,*) " Integeral:",Integeral

stop

End Program main