To find the approximate angle measure at vertex N in triangle LMN, we can use the cosine rule or the sine rule. In this case, we can use the sine rule which relates the angles and sides of a triangle.
Using the sine function, we'll find \(\sin(N)\):
\[ \sin(N) = \frac{\text{opposite}}{\text{hypotenuse}} = \frac{LM}{MN} = \frac{8}{10} = 0.8 \]
Now, we can find the angle \(N\) using the arcsin function:
\[ N = \sin^{-1}(0.8) \]
Calculating this gives:
\[ N \approx 53° \]
Thus, the approximate angle measure at vertex N is 53°.