Final answer:
The question lacks sufficient context to provide a specific measure for kl. It refers to trigonometry principles, which often use functions like cosine to determine lengths and measures in triangles.
Step-by-step explanation:
The question seems to be asking for the measure of a line or angle, likely within the context of geometry or trigonometry. Without the accompanying Figure 4.17 or 4.18 or additional context, it's challenging to provide a specific answer.
However, trigonometry often involves the use of sine, cosine, and tangent functions to determine the lengths of sides or measures of angles in right-angled triangles. For instance, if TL represents the length of a side and TR another side of a triangle, and we're given an angle, we could use the cosine function in the form TL = TR cos(θ) where θ is the angle. Without more context or the figure in question, I am unable to confidently provide the correct measure.