Corrections are by far the hardest to predict as their nature is usually unpredictable unless some obvious portion has already completed. However, there may still be further corrective action at hand once a corrective wave appears complete. Double combinations fit this description and they can contain a triangle for the ending wave structure. Identifying this triangle will help to understand the next move when complete.
Many Elliott Wave analysts will incorrectly assume the triangle is actually part of the next wave sequence (eg 1st and 2nd waves) or a wave 4, thus the count will be incorrect. Triangles appear regularly in corrections and it's beneficial to understand when and where they can occur.