In this study, we study on the length of bisector of angle by the method using the area, the method using the vector and the method using the similarity, also the length of trisector of angle by the method using the sine law, the method using the area and the method using the second law of cosine in triangle, respectively. And we study on the length of trisector of angle with the length of bisector in angle. This study is expected to use the learning materials for the interesting construction and the problem solving using trigonometric functions.