+0

# law of cosines

+5
390
2
+11
whats 400=169+121-286CosC . i keep getting 74.something and the answer is 112degrees37seconds? i can't find my calculator
nessapierce9  Jan 30, 2012
Sort:

#1
0
112.61986494804282480511 is what I come up with. Not sure how many decimals you need to round to, but that's it.

my final equation was:

C=acos((169+121-400)/286)
Guest Jan 30, 2012
#2
+6925
0

$$400 = 169 + 121 - 286\cos C\\ -286\cos C = 400 - 169 - 121\\ \cos C = -\dfrac{110}{286}\\ C = 112.6198649^{\circ} = 112^{\circ}37'11.51''$$

the arccosine of a negative number is in the range 90° < x $$\leqslant$$ 180°

MaxWong  Aug 21, 2016

### 22 Online Users

We use cookies to personalise content and ads, to provide social media features and to analyse our traffic. We also share information about your use of our site with our social media, advertising and analytics partners.  See details