(13a)
The curved surface area of a cone is given by A = πrl
Where l = slant height
Let A1 = A2 therefore
πr1L1 = πr2L2
r1 = 5cm, L1 = 12cm, L2 = ?
r2 = 6cm
Therefore π×5×12 = π×6×L2
L2 = 5×12/6 = 5×2 = 10cm

Draw the right angle triangle
h² = 10² – 6²
h² = 100 – 36
h² = 64
h = √64 = 8cm

(13bi)
A = [2 5] B = [3 -2] [-1 3] [4 1]

BA
=[3 -2][2 5] = [6+2 15+6] [4 1][-1 3] [8+-1 20+-3] =[8 21] [7 17]

(13bii)
|8 21|
|7 17|
= 8×17 – 7×21
= 136 – 147
= 11

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