# Homework Help: Angle of Vector

1. Jan 31, 2014

### xtrubambinoxpr

1. The problem statement, all variables and given/known data

Find Beta of <60,-50,40>

2. Relevant equations

Cosine β = Ay/lAl

3. The attempt at a solution

lAl = 87.74964387

So its arccos(-50/87.75) = 124.62

express to 2 significant figures and it keeps telling me im wrong. I rounded to 125. kept at 124.62.. etc.

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2. Jan 31, 2014

### xtrubambinoxpr

And i got the answer book telling me this

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3. Jan 31, 2014

### PhanthomJay

The book answers are clearly expressed to three significant figures. What is your correct response for the angle you determined expressed to two significant figures?

4. Jan 31, 2014

### xtrubambinoxpr

Online it tells me to do 2 sig figs.

5. Jan 31, 2014

### xtrubambinoxpr

And it's 125 degrees

6. Jan 31, 2014

### PhanthomJay

No, that is three significant figures. What is 124.62 degrees expressed to two significant figures??

7. Jan 31, 2014

### xtrubambinoxpr

I honestly don't know because it clearly has 3 at 125
How would I make that 2 sig figs

8. Jan 31, 2014

### PhanthomJay

I am not an expert on significant figure rules, but you can find them through Google and other search engines. But here is a hint: 141.635 rounded to four sig figs is 141.6. If rounded to three sig figs it is 142; that same number rounded to two sig figs is 140. And that same number rounded to one sig fig is 100.