Question

Law of cosines.Anyone good in Trigonometry?​

Answer 1

Answer:

$c=11.8\ units$

Step-by-step explanation:

we know that

The formula of law of cosines is equal to

$c^2=a^2+b^2-2(a)(b)cos(C)$

where

a, b and c are sides. C is the angle opposite side c

In this problem we have

$a=3\ units\\b=10\ units$

$C=120^o$

substitute the given values

$c^2=3^2+10^2-2(3)(10)cos(120^o)$

$c^2=109-(60)cos(120^o)$

$c^2=109-(60)(-0.5))$

$c^2=109+30$

$c^2=139$

$c=11.8\ units$