Real Life Applications of Cosine Law
Example 1
Example 2
a= 12 ft. + 5 ft. b= 26 ft. c= 8 ft. + 5 ft.
a= 17 ft. c= 13 ft.
b^2= a^2 +c^2-2ac Cos B
Cos B= (a^2 +c^2-b^2)/2ac
Cos B= (289+169-676)/442
Cos B= -218/442
Cos B= -0.49
B= inverse cos -0.49
B= 119.34°
Example 3
URBAN PLANNING The intersection of three streets forms a piece of land called a traffic triangle. Find the angle C.
Cos C= (a^2 +b^2-c^2)/2ab
Cos C= (28900+57600-122500)/2(170)(240)
Cos C= (86500-122500)/81600
Cos C= -36000/81600
Cos C= -0.44
C= inverse cosine -0.44
C=116.10°
Cos C= (a^2 +b^2-c^2)/2ab
Cos C= (28900+57600-122500)/2(170)(240)
Cos C= (86500-122500)/81600
Cos C= -36000/81600
Cos C= -0.44
C= inverse cosine -0.44
C=116.10°
(Retrieved from: http://www.muhsd.k12.ca.us/cms/lib5/CA01001051/Centricity/Domain/547/Trig/13-6%20Law%20of%20Cosines.pdf)