Trigonometric function is one of the elementary functions in mathematics, which is usually used to study triangles and modeling periodic phenomena. In a love relationship, when couples express their emotions with trigonometric functions, they may have the following meanings:

1. means that the other person is his whole world. This expression is common in "lim me→∞=you", which means "I am infinitely close to you" and expresses endless love for each other.

2. Express emotional interaction and sing. For example, "If I am sin and you are cos, then we only want Tan!" The trigonometric function in this case represents the emotional mutual understanding between two people.

Please note that these expressions may not be suitable for everyone or all situations, so the specific interpretation may vary according to the context and personal intention. If your partner uses such expressions, it's best to communicate with them directly to understand their real intentions.