In Triangle ABC, if a=3, b=5, and cosC=1/5, how do you find the exact value of c?

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Answer 1 · 2017-10-17T17:02:26

#c=2sqrt7#

we use the cosine rule

#c^2=a^2+b^2-2abcosC#

we have all the information required

so

#c^2=3^2+5^2-(2xx3xxcancel(5)xx1/cancel5))#

#c^2=9+25-6#

#c^2=28#

#c=2sqrt7#