- #1

Nightsheron

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## Homework Statement

First question:

The waves are approaching at an bearing of N70W, and at N50W, to a coast with a N13ºE orientation. What is the angle of the wave offshore?

Answer: 7 degrees and 27 degrees.

Second question:

The wave is approaching at an angle of 135º. The coast is at 305º. What is the angle of the wave offshore?

Answer: 80 degrees.

Third question (now the total confusion):

The beach is facing north-south. The wave is approaching at an angle of 277º, and 230º. What is the angle of the wave offshore?

Answers: 7º and 40º.

Fourth question:

The wave is breaking in a coast with a East-West orientation, having a N10E bearing. What is the breaking angle?

Answer: 10º.

Fifth question:

What is the incidence angle on open waters of a wave with a bearing of 130º, in a coast with a direction of 80º?

## Homework Equations

This is the formula we used at class:

Velocity of the wave offshore (as it is coming from the ocean) / Velocity of the wave when it is breaking = Sine of the angle of the wave offshore (as it is coming from the ocean) / Sine of the angle of the wave when it is breaking

## The Attempt at a Solution

First question:

Here's how I THINK the answer could have been achieved. I am just to convert the N70W to azimuth; it becomes 290, then I subtract 90 degrees until I get to a angle that is within 90º of the other one. Then I can subtract, that is, 20-13=7. But I do not know if this is the right method.

Second question:

My thinking: 305-90= 215 ; 215-135=80

Third question:

I don't know. If I use the above method, it works for the first angle, but the second angle would give me 50 degrees instead.

Fourth question:

This one seems straightforward but I am not going to assume anything!

Fifth question:

I don't know neither the answer nor how it is supposed to be done.

My teacher talked something about a projection, is it a orthogonal projection or...? He also talked something about drawing a perpendicular to a coast?

I can't find anything on the web that is similar so I can figure it out.

**PLEASE help.**If someone could give me the name of this kind of exercise, and some explained examples, I could try, but I haven't found much after hours of searching.

I have tried solving this, but I don't know if I am right or not.

I've been pulling my hairs for these ones! I have spent many a good hours on this, almost the entire day actually. If it didn't come through as I wrote the post, note the time here in Portugal is 4:30 AM. :(

Sorry if the wording seems odd, as I have translated it from Portuguese.

Thanks very much.