Posted by **Sam** on Wednesday, September 14, 2011 at 11:12am.

A rock, R, is 40 km from a harbour, H, on a bearing of 040°. A port, P, is 30 km from R on a

bearing of 130°.

Draw a sketch showing the points H, R and P and work out the size of angle HRP.

- Maths -
**Reiny**, Wednesday, September 14, 2011 at 11:32am
I hope you made the sketch.

I have a nice right-angled triangle HRP

with angle R = 90° , HR = 40, RP = 30

- Maths -
**Sam**, Wednesday, September 14, 2011 at 11:37am
Thanks.

Could you tell me the angles for H and P

R= 90

H= ?

p = ?

- Maths -
**Reiny**, Wednesday, September 14, 2011 at 11:54am
use simple trig

for angle H

tanH = opposite/adjacent

= 30/40 = .75

angle H = appr.36.9°

then by simple subraction, angle P = 90-36.9 = 53.1°

use 2nd Tan on your calculator

(tan inverse or arctan, depending on your calculator

on mine I do:

2ndF

tan

.75

=

to get 36.869...

- Maths -
**Sam**, Wednesday, September 14, 2011 at 12:03pm
Thanks.

- Maths -
**Sam**, Wednesday, September 14, 2011 at 12:21pm
Can you tell me the bearing of P from H?

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