Question

Law of cosines.Anyone good in Trigonometry?​

Answer 1

`c=11.8\ units`

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`