Posted by **jonathan** on Sunday, February 24, 2008 at 9:16pm.

Two ships, one sailing at 30 km/hr and the other at 45 km/hr, left port at the same time. Three hours later they were 120 km apart. If you had to find the angle between their courses an equation that could be used to solve this problem is:

- trig -
**Reiny**, Sunday, February 24, 2008 at 9:24pm
looks like a straightforward application of the cosine law.

120^2 = 90^2 + 135^2 - 2(90)(135)cosß

where ß is the angle between them

- trig -
**Damon**, Sunday, February 24, 2008 at 9:24pm
Ship A went 30 * 3 = 90 km

Ship B went 45 * 3 = 135 km

So we have a triangle with legs of 90 and 135 and an opposite side of 120

Use the law of cosines

120^2 = 90^2 + 135^2 - 2*90*135 cos T

solve for T

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