The length of AB in the triangular prism is 6.58 cm
How to find the length
The length is sought using trigonometry
You have to know that FB = EC = 15 cm. This is the hypotenuse
Using sin trigonometry, we have
sin 26 = AB / FB
sin 26 = AB / 15
AB = 15 * sin 26
AB = 6.5756
AB = 6.58 cm (to2 decimal place)