the diagram shows a cone.
the radius of the base of the cone is 10cm
the slant height of the cone is 15cm
(a) work out the total surface area of the cone. ??????
The area of a cone formula is $\displaystyle A = \pi r \sqrt{r^2+h^2}$ but you would use that if you were given the height of the cone, not the length of the slant side of the cone as in your problem. So you need to find the height of your cone.
To determine the height of your cone:
Since you are given the length of the slant side, you need to find the height of the cone itself. A cone is made from a right triangle that is rotate around itself, right? You are given one of the legs of the triangle, it is the radius of your cone. You are also given the length of the hypotenuse (the slant side). Use the Pathagorean theorum $\displaystyle (a^2 + b^2 = c^2) $to find the height of the triangle which is also the height of your cone. Then you can use the formula for the area of a cone to find your answer.
Remember that a & b of your Pathagorean equation are the legs, and c is your hypotenuse.
Does this make sense? Good luck!
This is not a formula for a calculator. This is how you do the problem. It is not our job to answer the question for you. None of us is getting paid to help you. You should thank people that try to help you instead of complaining about the help you have been given.
This is Math HELP Forum, not Math ANSWERS Forum.
Duplicate question posted here: http://www.mathhelpforum.com/math-he...area-cone.html
This thread is closed - I can't be bothered trying to merge the two threads into anything semi-coherent.