Answer:
<h2>C.</h2>
Step-by-step explanation:
In the given graph, we have an isosceles triangles, which height divides its side in two equal parts.
So, from the division, we have to equal right triangles, which on leg is 6, and its angle is 80°, being the height the other leg.
Now, to find the height, we have to use trigonometric reasons, specifically, the tangent reasons because involves a relation with both legs

So, we isolate
to find its expression

If we compare with given choices, you'll observe that option C is the right answer.