Question

Find the indicated angle or side. Give an exact answer.

Answer 1

To answer this question we will use the Cosine Law:

`a^2=b^2+c^2-2bc\cos A.`

Substituting b=2, c=4, and A=60º in the above equation we get:

`a^2=2^2+4^2-2*2*4\cos60º.`

Simplifying the above result we get:

`\begin{gathered} a^2=4+16-16*(1)/(2) \\ =4+16-8=12. \end{gathered}`

Therefore:

`a=√(12)=2√(3).`

Answer:

`a=2√(3).`