# Trigonometry Triangle Help

1. Aug 22, 2007

### blueparukia

First off, I was just moved up a grade (about 2 week ago) and the class is studying trigonometry.

1. The problem statement, all variables and given/known data
I have a triangle:
Hyp = 10m
Opp = 4m
Feta = Unknown

And I need to find feta.

2. Relevant equations
???

3. The attempt at a solution
Well, I have tried a lot of random things lol.
E.g: sin-1 (10x4)

I also have another question. Exactly from the revision sheet.
By using a radar beam. an observer at A determinses that a plane at B is 2000 metres away (AB=2000) Use the information given to calculate the height of the plane above the horizontal $$\overline AC$$ The angle is 50 degrees. I know the answer is 2000xsin 50, but how do I know t is sin? The teacher gave me the answer, but I dunno how she came up with sin :(

BP

Last edited: Aug 22, 2007
2. Aug 22, 2007

### HallsofIvy

Staff Emeritus
In order to do that, you first need to know the definitions of sine, cosine, etc!

sine is defined, in a triangle,as "opposite/hypotenuse", NOT "opposite times hypotenuse. You need to find sin-1(4/10).

3. Aug 22, 2007

### blueparukia

4/10 thank you!!!!!!!! I was using 4x10. Completely forgot.

Thankl you,

BP