Because the angle alpha = 60 degrees,

So the angle ABD=30 degrees,

So AD=AB/2= 15/2cm, BD= (root number 3)AD= 15 (root number 3)/2cm,

So CD = AC-AD = 33/2 cm,

So BC= root sign (BD 2+CD 2)

= root sign (1464/0)

= number of roots is 366cm.

22。 According to the meaning of the question, the angle AOB=32 degrees +58 degrees =90 degrees, OA=30X5= 150 nautical miles, OB=40X5=200 nautical miles,

So we can get from Pythagorean theorem: AB= root sign (OA 2+OB 2).

= root sign (150 2+200 2)

=250 nautical miles

That is, at 1 in the afternoon, the two ships were 250 nautical miles apart.

23。 Because the circumference of the bottom of the round tank is12m and the height is 5m,

Therefore, the length (rectangle) of the side development diagram of the round tank is 12m, and the width is 5m.

So from the Pythagorean theorem:

The diagonal length of the side development diagram of the round tank is: 13m,

That is, the shortest ladder is 13m.