The slant height is read from the diagram as 20.1 km.
The radius is half the diameter, so is 9.0 km.
The lateral area is ...
A = πrs = π(9.0 km)(20.1 km) ≈ 568.3 km²
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Desmos uses r for a special purpose, so we have used r₁ to signify the radius of the cone. The "round" function works only to round to an integer, so special effort must be used to get rounding to 1 decimal place.
Since we know that both sides, a and b are equal to 2, and angleA is equal to 30°, we can conclude that angle B is also equal to 30°. Also, we can know that the other angle (C) will be equal to 120° since the sum of all the angles in a triangle will be always equal to 180°.
1st element can be matched with 5 2nd element can be matched with 4 3rd element can be matched with 3 etc. Total number of correspondences = 5*4*3*2*1 = 120