Trig

posted by Isaac

A ship leaves port at 6 am and heads due east at 20 knots. At 10 am, to avoid a storm the ship changes course to N 47° E.. (47° east of north). Find the ships distance from port at 4 pm.

1. Reiny

first path:
4 hrs at 20 knots = 80 n miles

second path:
6 hrs at 20 knots = 120 n miles
angle between them = 90+47 = 137°

I see a clear case of the cosine law:
let x be the distance from port

x^2 = 80^2 + 120^2 - 2(80)(120)cos137
= ....
x = √....

you do the button-pushing

2. Isaac

Sorry what do you mean by ^ ?

3. lufet

186.66 miles

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