Pre-Calculus - Learn How To Evaluate The Double Angle for Sine Given a Triangle

The video tutorial explains how to find the sine of 2U given U equals -2/sqrt(5). It starts by identifying the triangle and determining the quadrant. The tutorial then constructs the triangle, calculates the opposite side, and uses trigonometric formulas to find the sine of 2U. The process involves understanding the relationship between sine and cosine in the second quadrant and applying the double angle formula.

Explain the formula used to find the sine of double the angle.

What values do you obtain for sine and cosine of the angle U?