Answer:
[tex]a=2\sqrt{3}[/tex]
Step-by-step explanation:
Side a is the side opposite angle A.
Side b is the side opposite angle B.
Side c is the side opposite angle C.
We have been given the lengths of 2 sides and the included angle.
Therefore, to find side a use the cosine rule.
Cosine rule
[tex]a^2=b^2+c^2-2bc \cos A[/tex]
where:
- a, b and c are the sides
- A is the angle opposite side a
From inspection of the triangle:
- side b = 2
- side c = 4
- angle A = 60°
Substitute the given values into the formula and solve for a:
[tex]\implies a^2=b^2+c^2-2bc \cos A[/tex]
[tex]\implies a^2=2^2+4^2-2(2)(4) \cos 60^{\circ}[/tex]
[tex]\implies a^2=4+16-16\left(\dfrac{1}{2}\right)[/tex]
[tex]\implies a^2=4+16-8[/tex]
[tex]\implies a^2=12[/tex]
[tex]\implies a=\sqrt{12}[/tex]
[tex]\implies a=\sqrt{4 \cdot 3}[/tex]
[tex]\implies a=\sqrt{4}\sqrt{3}[/tex]
[tex]\implies a=2\sqrt{3}[/tex]
Therefore, the exact length of side a is 2√3.
