Using Your Left Hand to Find Sine and Cosine Values

Miacademy & MiaPrep Learning Channel

This instructional math video introduces a powerful mnemonic device called the "Left-Hand Technique" for memorizing trigonometric values. The host, Justin, transitions from the previous lesson on special triangles to this more efficient method for finding exact values of sine and cosine for first-quadrant angles (0, 30, 45, 60, and 90 degrees). The video demonstrates how to use the fingers of the left hand to represent specific angles and how to count fingers to populate the standard formula for these trig functions. The content focuses on recognizing patterns in trigonometric values, specifically that they all follow the structure of the square root of a number divided by two. It breaks down the physical setup of the hand trick: the pinky represents 0 degrees, moving up to the thumb at 90 degrees. The video provides step-by-step examples for 30, 45, and 60 degrees, clearly distinguishing between counting fingers "above" the bent finger for cosine and "below" for sine, supported by an alphabetical mnemonic. For educators, this video serves as an excellent intervention for students struggling with rote memorization of the unit circle. It offers a kinesthetic and visual alternative to the traditional table or special triangle methods. The video is practical and direct, making it a perfect resource for Algebra II, Geometry, or Pre-Calculus classrooms to help students gain fluency in recalling trig values quickly during tests or problem-solving exercises.