## Algebra and Trigonometry 10th Edition

$-1\leq sin~θ\leq1$ $0\leq\sqrt {1-cos^2θ}\leq1$ Example: $θ=225°$: $sin~225°=-\frac{\sqrt 2}{2}\ne\sqrt {1-cos^2225°}=\sqrt {1-(\frac{\sqrt 2}{2})^2}=\frac{\sqrt 2}{2}$
$sin^2θ+cos^2θ=1$ $sin^2θ=1-cos^2θ$ $sin~θ=±\sqrt {1-cos^2θ}$