Mathematics coaching can have a positive impact on classroom teaching practices and outcomes for students, and there is a demonstrated need for improvement in mathematics teaching. This qualitative study examined the practices of three middle school mathematics coaches implementing the "Responsive Teaching Cycle" ("RTC"), a budding new approach to coaching. The math coaches were part of a U.S. Department of Education Investing in Innovation (i3) grant-funded project with California State University Northridge called Collaboration Resulting in Educators Applying Technology Effectively (CREATE). Teachers collaborated with an RTC coach and other grade-level teachers and were supported in the use of technology to aid in the design of learning activities. Data collection and analysis painted a picture of teacher-coach relationships through an open-ended questionnaire, document analysis, observations of coaches with their teachers, and individual interviews with coaches and their teachers. These data were analyzed and discussed to provide a rich description of teacher-coach relationships in RTC coaching to give insight to building trust within these relationships. This study of trust-building in the context of RTC coaching provided rich descriptions of trust in action that supplied valuable insights to this model as well as learnings and additional questions that extend beyond its boundaries. The results of this study confirm prior findings on trust in that trust was found to be influenced by a number of factors in varied combinations within the examined relationships. This study supports the literature finding that trust changes over time. The relative absence of trust-building symbolic acts carried out by coaches is incongruous with the literature and represents a strength of RTC. RTC holds promise as a coaching model that builds trust while building teacher capacity. When implemented with fidelity, RTC coaches build trust as they engage teachers in meaningful coaching conversations. Coaching practices observed and described herein can be incorporated by coaches outside the studied context. Concrete examples of trust in coaching relationships help inform current practice for coaches and coach trainers. It is my hope that this work contributes to the improvement of student outcomes by aiding in the development teachers through expansion of a nascent coaching model. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]