See Jabez Tay's answer to Nigel's Secondary 4 E Maths Singapore question

Jabez Tay's answer to Nigel's Secondary 4 E Maths Singapore question.

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You can work backwards from the volume of a cone equation.

h= the radius of the larger circle
r= base radius, answer you found in the previous part.

Hope it helped you! If you still don’t understand or need help, you can contact me at j_a_b_e_z@yahoo.com.sg!

Date Posted: 5 years ago

Comments 4 add a comment

Jabez Tay

5 years ago

If you know how to get the angle ACD, you can use cosACD and AC=5 to obtain the base radius

Nigel

5 years ago

In that case, can you show me how to work out the previous part (b)(i) and (b)(ii) as well as I am not able to understand with just the formula list?

Jabez Tay

5 years ago

I’m out now, so it’s abit hard to write on paper.

But if you can understand these three equations, you will be able to solve b(i) and b(ii)!

b(i) cosACD=base radius/AC

b(ii) sinACD=h/AC

Volume of cone=1/3(pi)(base radius)^3(h)

Best I can do now ps. If you can have the answer later I can write for u at night.

5 years ago

These steps are for the 'cone' CAD. (Which is actually not a cone as the segments are flat on the paper and not actually orthogonal to the perpendicular from A to CD)

The question is actually asking for the cone formed when sector CED is folded into a large cone by joining AC and AD together