Final answer:
Diagonal subsections are commonly taken when cutting a triangular graduation haircut to build weight and create a smooth blend of lengths for a layered effect.
Step-by-step explanation:
When cutting a triangular graduation haircut, the types of subsections typically taken are diagonal subsections. This method involves parting the hair in a way that creates a diagonal angle with respect to the head, allowing for a soft graduation and a layered effect. This technique helps to build weight and create a smoother blend between the different lengths of hair within the haircut.
It's important to note that the direction of the diagonal subsections can vary depending on the desired outcome of the hairstyle. Stylists may choose to cut the hair diagonally forward or backward to achieve specific angles and layers in the finished haircut.