Explore a comprehensive 21-minute video tutorial on trigonometry, focusing on essential concepts for calculus. Learn about unit circle definitions, the importance of radians, and how to graph cosine and sine functions. Discover special triangles, compute unusual trigonometric values, and understand the geometric meanings of secant and tangent. Delve into Pythagorean identities, trigonometric identities, and witness a geometric proof of the sum rule. Gain a deeper understanding of trigonometry, enabling you to derive formulas independently and apply them effectively in calculus and beyond.