In this study, we presented MathTOUCH, a rich-text editor, to create mathematical documents. In mathematics e-learning with learning management systems, existing math input methods have heavy workloads; therefore, math notations are a long-standing challenge. Furthermore, when creating mathematical documents, such as writing reports and posting questions on the forum, users must enter both texts in a natural language input manner and mathematical expressions in a math input manner. Hence, users' workload increases. To address this issue, we developed the MathTOUCH editor to implement an intelligent math input interface that enables users to enter equations through predictive conversion from the colloquial-style text. A user study was conducted with 71 participants to evaluate the effectiveness of the proposed editor. The results indicate that users could enter equations with the MathTOUCH editor approximately 1.5 times faster than with a standard interface, and the participants also reported greater subjective satisfaction.