Question

The height h of the equilateral triangle below is given by y= 5 cot theta where theta = 30 degrees

Answer 1

To solve this we can take two different approaches:

1. We can substitute theta by 30° and evaluate our expression using a calculator: 
$y=5cot( \alpha )$
$y=5cot(30)$
$y=8.7$

2. We can use the unitary circle and the fact that $cot \alpha = \frac{cos( \alpha }{sin( \alpha )}$, so we can rewrite our expression as follows:
$y=5cot( \alpha )$
$y=5 \frac{cos( \alpha )}{sin( \alpha )}$
$y= \frac{cos(30)}{sin(30)}$
From our unitary circle we can check that $cos(30)= \frac{ \sqrt{3} }{2}$ and $sin(30)= \frac{1}{2}$. 
Lets replace those values in our expression and simplify:
$y= \frac{ 5(\frac{ \sqrt{3} }{2})}{ \frac{1}{2} }$
$y=5 \sqrt{3}$
$y=8.7$

Either way we can conclude that the correct answer is: D)8.7