Answer:
1.5 cm
Explanation:
The lateral area is given by ...
LA = πrh
86 cm^2 = π(18 cm)h
h = (86 cm^2)/(18π cm) ≈ 1.5 . . . cm
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Comment on the problem
The geometry described here is impossible. The slant height cannot be less than the radius of the cone. We suspect a typo in the problem statement.