Basic Trig Identities
Next let's see how these functions are related. In the video, we
explain the following identities:
- sin(π2−θ)=cos(θ)
- cos(π2−θ)=sin(θ)
- sin(−θ)=−sin(θ)
- cos(−θ)=+cos(θ)
- sin(π2+θ)=cos(θ)
- cos(π2+θ)=−sin(θ)
- sin2(θ)+cos2(θ)=1
- tan2(θ)+1=sec2(θ)
- 1+cot2(θ)=csc2(θ)
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The last three are called Pythagorean identities, since they're
all based on the Pythagorean theorem.
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