# Two scouts are in contact with home base. Scout A is 15 km from home base in a direction 30 degrees north of east. Scout B is 12 km from home base in a direction 40 degrees west of north. How far is scout B from scout A?

Scout A, home base and a point directly south A form a right triangle with a 15 km hypotenuse and an interior angle of 30 degrees.  Scout A is `15 sin 30` km north, or 7.5 km.  The scout is `15 cos 30` or 13km East.

Scout B, home base and a point directly north from home base form another right triangle with a hypotenuse of 12 km and an interior angle of 40 degrees.  The scout is `12 cos 40` or 9 km North, and `12 sin 40` West.

From this information we can calculate the distance along North-South line between the two scouts is 9-7.5=1.5 km, and we can calculate the distance along East-West line between the two scouts is 13+8=21km.  These lines are at right angles, so the straight line between A and B is the hypotenuse of a right Triangle with legs of 1.5 km and 21km.  The Pythagorean theorem says that this hypotenuse will be `sqrt(21^2+1.5^2)=sqrt(441+2.25)~~21.05`

Scouts A and B are approximately 21.05 km apart.

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