Question

Find the measure of angle A in degrees.Option 1: 135°Option 2: 140°Option 3: 120°Option 4: 60°

Answer 1

To solve this problem, we use the Law of Cosines.

Using the Law of Cosines, we get that:

`2√(13)=√(2^2+6^2-2(2)(6)cosA).`

Solving the above equation for cosA, we get:

`\begin{gathered} 4(13)=4+36-24cosA, \\ 52=40-24cosA, \\ 24cosA=-12, \\ cosA=(-12)/(24)=-(1)/(2). \end{gathered}`

Therefore:

`A=120^(\circ).`

Answer:

`\begin{equation*} 120^(\circ). \end{equation*}`