Visualize the image in your mind and you can see that it forms a right angled triangle with a base,altitude and hypotenuse
base=2 feet
hypotenuse(ladder)=13 ft
We need to find the altitude,
By applying pythagoras theorem,
base square+altitude square=hypotenuse square
Take altitude as x
2 square+x square=13 square
4+x square=169
x square=169-4
x square=165
x= root of 165
x=12.8 feet(approx.)
