Abstract: The image of the triangular conforms to the aesthetic intention of harmony of the learning subject. This aesthetic intention of harmony will prompt the learning subject to recognize that the mathematical symbols expressing the triangle must also conform to the aesthetic intention of harmony. This is the proportion formed by the cosine of the triangle and the ratio of the opposite side, which has the harmonious form expression of the sine theorem. The method of proving the proposition constituted by this expression to be a true proposition must also be a method that conforms to the aesthetic intention of harmony and integrity. These understandings provide an effective method for mathematics teachers to design and implement the teaching of the sine theorem in the classroom, thereby enhancing the effectiveness of mathematics classroom teaching.