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Explore which trig functions are even (symmetric about y-axis) and which are odd (origin symmetric).
Memory tip: Cosine (and its reciprocal secant) are even - they start with "co" or "se" and are "even". All others are odd.
Symmetric about y-axis
Symmetric about origin
An even function has f(-x) = f(x) (same y-value for opposite x). An odd function has f(-x) = -f(x) (opposite y-value). This relates to polynomial degrees: x² is even, x³ is odd.
They help simplify expressions with negative angles. For example, sin(-30°) = -sin(30°) = -0.5, without needing to compute anything new.
Think of the unit circle: cos is the x-coordinate (same for ±θ), sin is the y-coordinate (flips sign for -θ). Or remember "cosine is even, sine is odd".