# Thread: non right angle trig

1. ## non right angle trig

A tanker is moving 5 nautical miles (5 knots) on bearing 105 degrees.at 1100 hours (11am) the tanker obserbs a lighthouse on bearing 040 degrees. at midday the lighthouse bears 340 degrees. Draw a well labelled diagram to show the movement of the tanker between 11am and midday. calculate the distance in nautical miles from the tanker to the lighthouse at midday.

I know the angle LH is 40 degrees
but i still get confused in finding the angles for P1200 and P1100.
The length from P1100 to P1200 is 5nm. I use the SIN rule for non right angle trig.
so
SIN 5nm SIN ??????
sin 40degrees equals sin ??????
How do I work this out?
I need the answer 12 hours from now
thanks.

2. Originally Posted by mat
A tanker is moving 5 nautical miles (5 knots) on bearing 105 degrees.at 1100 hours (11am) the tanker obserbs a lighthouse on bearing 040 degrees. at midday the lighthouse bears 340 degrees. Draw a well labelled diagram to show the movement of the tanker between 11am and midday. calculate the distance in nautical miles from the tanker to the lighthouse at midday.

I know the angle LH is 40 degrees
but i still get confused in finding the angles for P1200 and P1100.
The length from P1100 to P1200 is 5nm. I use the SIN rule for non right angle trig.
so
SIN 5nm SIN ??????
sin 40degrees equals sin ??????
How do I work this out?
I need the answer 12 hours from now
thanks.
let lighthouse be point L

1100 position ... point A

1200 position ... point B

$\displaystyle m\angle A = 65$

$\displaystyle m\angle B = 55$

$\displaystyle m\angle L = 60$

use the law of sines ...

$\displaystyle \frac{LB}{\sin(65)} = \frac{AB}{\sin(60)}$