Lampe overfladeareal

#lavet af steven

lastvol = 0

grænse = 1005

f = function(x){ #f(x)
  y <- (-x^2+20*x)^(1/2)
  return(y)
}


t = function(x){ #f'(x)
  y <- 1/(2*(-x^2+20*x)^(1/2))*(-2*x+20)
  return(y)
}


p = function(x){ #f(x)
  y <- f(x)*(1+t(x)^2)^(1/2)
  return(y)
}

h = seq(15.99, 20, 0.000001)


for(i in 1:length(h)){


vol = (integrate(p, 0, h[i]))

vol = vol$value*2*pi

print(vol)





if(lastvol < grænse & vol >= grænse){
  print("result!")
  print(h[i])
  break()

}
  lastvol = vol
}