Answer :

Step-by-step explanation:

here,,

a=3,b=10,C=120°

c^2=a^2+b^2-2ab cos120°

=(3)^2 +(10)^2 _2 (3)(10)(-1/2) [cos120°=-1/2]

=9+100-(-30)

=109+30

=139

c=(139 )1/2=11.79

c=12

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