C++ Arithmetic Operator Calculating the height of a tree

#include <iostream>
#include <iomanip>
#include <cmath>

int main()//from  w w  w  . j  a v a2  s.c o  m
{
  const double inches_per_foot = 12.0;
  const double pi {3.14159265};
  const double pi_degrees {180.0};
  double d_feet =0;
  double d_inches =0;
  double angle =0;
  double eye_height =0;

  std::cout << "Enter the distance from the tree in feet and inches: ";
  std::cin >> d_feet >> d_inches;
  double distance {d_feet + d_inches / inches_per_foot};

  std::cout << "Enter the angle of the top of the tree in degrees: ";
  std::cin >> angle;
  angle *= pi/pi_degrees; // Convert angle to radians

  std::cout << "Enter your eye height from the ground in inches: ";
  std::cin >> eye_height;

  eye_height /= inches_per_foot;    // Convert to feet

  double height {eye_height + distance*std::tan(angle)};// Tree height in feet

  double height_feet {std::floor(height)};

  double height_inches {std::floor(inches_per_foot*(height - height_feet) + 0.5)};

  std::cout << "\nThe height of the tree is " 
            << height_feet << " feet " 
            << height_inches << " inches.\n" << std::endl;
}