Instant Points
Trigonometry
Complementary Trig Theorem
\[ \sin(x) = \cos(90 - x) \]
Sine and Cosine are "Co-functions". They are equal when their angles sum to 90 degrees (or \(\pi/2\) radians).
📝 Example: Basic Complement
If \(\sin(x) = 0.8\), then \(\cos(90-x)\) is also \(0.8\). No calculator needed.
📝 Example: Radian Complement
\(\sin(\pi/6) = \cos(\pi/2 - \pi/6) = \cos(\pi/3) = 0.5\).