How do you solve #c^2=12^2+10^2-2(12)(10)cos40#?

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Answer 1 · 2018-04-08T05:40:57

#color(brown)(c = 7.76#

#c^2 = 12^2 + 10^2 - 2 * 12 * 10 * cos 40#

#c^2 = 144 + 100 - 240 cos 40#

#c^2 = 244 - 240 cos 40#

#c^2 = 244 - 183.85 = 60.15#

#c = +- sqrt(60.15) = +- 7.76#

As c cannot be negative,

#color(brown)(c = 7.76#