The cosine is known as an even function, and the sine is known as an odd function. Generally speaking,
f(x) is an even function if f(-x) =f(x)
and odd if f(-x) = -f(x)
The cosine and sine functions satisfy the following properties of symmetry:
cos(-θ) = cos(θ) => symmetry about y-axis
sin(-θ) = -sin(θ) => symmetry about origin
also
tan(−θ)=−tan(θ)=> symmetry about origin
cot(−θ)=−cot(θ)=> symmetry about origin
csc(−θ)=−csc(θ)=> symmetry about y-axis
sec(−θ)=sec(θ)=> symmetry about y-axis
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