Answer:
That is a right angles triangle which means to get the area: multiply the base(14.1)to be the height (9.8) divided by 2.
Formula : half the base times the height given. Your answer is to be squared and don't forget the correct unit.
The lateral area of the pyramid is 15!
You can use the trigonometric identity

.

The requirement that

eliminates -1/6 from being another solution.
Check the picture below.
includes 2, notice, it doesn't go below 2 over the y-axis, and then it keeps on going up. So, the range is from +2 onwards.