You may only use elementary geometry, such as the fact that the angles of a triangle add up to 180 degrees and the basic congruent triangle rules (side-angle-side, etc.).

To the problems that have been for long about matching methods, this paper presents a new one based on congruent triangle and makes a detailed presentation about the composing of congruent triangle.

Dubbed the "Google Golden Triangle" because the concentration of eye gazes tended to be top and left, the results are congruent with the F-shaped pattern seen in Nielsen’s independent research.