Notice that with the information given, we can make a simple schematics of a right angle triangle for which we know an acute angle, a leg, and are asked to find the other leg of the triangle (or the hypotenuse, since the word "line of sight is not used properly in the text of the problem). The schematics is shown below:
The other leg of the right triangle is pictured in red in the image, if it is what the problem is asking (LINE OF SIGHT DISTANCE, which is always understood as a horizontal reference).
So we can use the tangent function to solve this case, as shown below
[tex]\begin{gathered} \tan (14\circ)=\frac{300}{d} \\ d=\frac{300}{\tan (14)}\approx1203.23 \end{gathered}[/tex]
which tells us that the horizontal distance between camera and end of the field is approximately 1203.23 meters.
In the case that the problem is asking for the slant distance between the camera and the end of the field, we need to find the HYPOTENUSE of the right angle triangle (pictured in orange in the image above), and in such case we use the sine function as shown below:
[tex]\begin{gathered} \sin (14)=\frac{300}{\text{hyp}} \\ \text{hyp}=\frac{300}{\sin (14)}\approx1240.07 \end{gathered}[/tex]
Which tells us that the slant distance between camera and the end of the field is about 1240.7 meters
From the drawing you sent, it looks more like the teacher may be asking for the slant distance. So please use the second answer : 1240.7 meters.
Please remind you teacher that the standard use of "line of sight" is to represent the horizontal line from which the angle of elevation or angle of depression is measured. So it is not appropriate to use the term in the context it has been used.
