## anonymous one year ago Getting another Calculator Error Cosine Law Trig Here is the problem A = 103 degrees Sides are b =31 c=52 Equation $$a^2 = 31^2+52^2-2\times 31 \times 52$$ = a = 66.2589 $$\large \cos B = \frac{66.25^2 +52^2-31^2}{2\times 66.25\times52}$$ Am I right so far?? Do you get an error?

1. AbdullahM

Where is cos(A) in the equation?

2. AbdullahM

$$\sf a^2 = 31^2+52^2-2\times 31 \times 52 cos(103)$$ = 66.2589

3. AbdullahM

Oh nevermind, you forgot to put cos(103) but you arrived at the correct a value.

4. anonymous

Did I forget to square that??

5. AbdullahM

$$\sf a^2 = 31^2+52^2-2\times 31 \times 52 cos(103)$$ then a=66.2589 not a^2, my bad.

6. anonymous

Ok cool. Do you get an error on your cal??

7. anonymous

$$\huge B =\cos^{-1}( \frac{66.25^2 +52^2-31^2}{2\times 66.25\times52} )$$ I get an error

8. anonymous

Crap it worked this time........ I got 27.12

9. AbdullahM

So now we have: A= 103 degrees a = 66.26 b=31 c=52 Using sin laws $$\sf\Large \frac{sin103}{66.26} =\frac{sinB}{31}=\frac{sinC}{52}$$ So we want to solve for $$\sf B$$. $$\sf\Large \frac{sin103}{66.26} =\frac{sinB}{31}$$ Cross multiply $$\sf\Large sin(103) \times 31 = Sin B\times 66.26$$

10. AbdullahM

Yes, 27.12 is the correct value for B :)

11. anonymous

That is strange..... I did not do anything . I just hit my back button to bring it up again and then hit enter and it gave me the answer. LOL

12. anonymous

Wierd.... Stuff is going to drive me batty

13. AbdullahM

Calculators are evil lol

14. anonymous

Thanks for the help. :-)

15. AbdullahM

Anytime :)

16. AbdullahM

Once you get the hang of the questions, it will become more easier xD