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# C4 june 2015 integration question Watch

1. https://a086a5a2f39bda93734c56a63fab...%20Edexcel.pdf

Hi, for the last question how would you know what the radius and height is for the cone?
2. (Original post by imran_)
https://a086a5a2f39bda93734c56a63fab...%20Edexcel.pdf

Hi, for the last question how would you know what the radius and height is for the cone?
Say R is the point on the x-axis vertically below P. Then the cone is formed by rotating the triangle PQR 360 degrees about the x-axis.

Try and imagine rotating this triangle and think about how the cone is formed.

Post your thoughts if you're still unsure.
3. The radius is the y coordinate and the height is the difference in the x coordinates. I just picture the shape rotating about the x axis.
4. integrating the equation y=3^x will get you the equation of R+S

You can then find out the area of S by saying its a cone, made up of radius = 9 and height = 2- (x-coordinate of Q)

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