TanC=3 times the root number 7.

So c is an acute angle.

Multiply sinC/cosC=3 times the root number 7.

de(sinc)2 = 63(cosc)2 = 1-(cosc)2

So (cosc) 2 = 1/64,

cosC= 1/8

(2)

From a+b=9 and a*b*cosC=ab* 1/8=5/2.

a*b=20

So a 2+b 2 = (a+b) 2-2ab = 4 1.

According to cosine theorem

c^2=a^2+b^2-2*ab*cosc=4 1-40* 1/8=36

So c=6