Question

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?

Answer 1

Where is cos(A) in the equation?

Answer 2

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

Answer 3

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

Answer 4

Did I forget to square that??

Answer 5

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

then a=66.2589

not a^2, my bad.

Answer 6

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

Answer 7

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

I get an error

Answer 8

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

Answer 9

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

\(\sf\Large sin(103) \times 31 = Sin B\times 66.26\)

Answer 10

Yes, 27.12 is the correct value for B :)

Answer 11

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

Answer 12

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

Answer 13

Calculators are evil lol

Answer 14

Thanks for the help. :-)

Answer 15

Anytime :)

Answer 16

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