[waqarasim]

hello tsr,
in this past paper there are only 2 questions which i dont understand, can anyone help please?

they are all of qestion 25 and 26b. ive seen the mark scheme and its doesnt really help me understand so i was hoping someone could go through it for me?
thanks

http://www.edexcel.com/migrationdocu...e_20110606.pdf

[notnek]

25. The curved surface area of a cone is where r is the radius and l is the slanted height. So the total surface area is this plus the area of the circular base. So we have




The surface area of a sphere is so the surface area of a hemisphere is half of this plus the area of the circular base:




The question says that the two surface areas are equal so you can equate the two SA expressions above. Then cancel and rearrange to find l in terms of x.

Finally, use Pythagoras to find l in terms of x and h then rearrange.

[notnek]

26b. P lies on AB with a distance ratio of 2:3 so .

Does this help? If you're still stuck, post any ideas/working that you have.

[waqarasim]

thanks so much
why use pythagoras in 25? thats for triangles

[notnek]

(Original post by waqarasim)
thanks so much
why use pythagoras in 25? thats for triangles

The shape in the cone made using the lines x, h and l is a right-angled triangle since the height is perpendicular to the base.

[waqarasim]

Ok thanks