# Math Help - Simple Trig Problem Which I Can't Seem To Get!

1. ## Simple Trig Problem Which I Can't Seem To Get!

Hey guys

A lighthouse is 10 km north-east of a ship travelling due west at 16 km/h.

i) How far is the ship from the lighthouse 45 min later?

ii) What is the bearing of the light-house from the ship at this time?

For i):

I used the cosine side formula…

$
LB^2 = 10^2 + 12^2 - 2(10)(12)cos45$

$LB = 8.6 cm
$

Which is wrong because the answers say it’s 20.3 km.

For ii):

I used the cosine angle formula:

cos $\angle$B = 55 degrees
Bearing = 270 + 55
=325 degrees T
Which is also wrong according to answer (070 degrees T)