A growing body of literature has identified quantitative and covariational reasoning as critical for secondary and undergraduate student learning, particularly for topics that require students to make sense of relationships between quantities. The present study extends this body of literature by characterizing an undergraduate precalculus student's progress during a teaching experiment exploring angle measure and trigonometric functions. I illustrate that connecting angle measure to measuring arcs and conceiving the radius as a unit of measure can engender trigonometric meanings that encompass both unit circle and right triangle trigonometry contexts. The student's progress during the teaching experiment also indicates that a covariation meaning for the sine function supports using the sine function to represent emergent relationships between quantities in novel situations.