sinθ = ac
cosθ = bc
tanθ = ab
cscθ = ca
secθ = cb
cotθ = ba
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Trigonometric Functions
Knowledge
Trigonometric functions: (also called circular functions, angle functions) are real functions which relate an angle of a right-angled triangle to ratios of two side lengths.
Relationship
sinθ = cos(π2 - θ) = 1cscθ
cosθ = sin(π2 - θ) = 1secθ
tanθ = sinθ cosθ = cot(π2 - θ) = 1cotθ
cotθ = cosθ sinθ = tan(π2 - θ) = 1tanθ
secθ = csc(π2 - θ) = 1cosθ
cscθ = sec(π2 - θ) = 1sinθ
Example
Find the x value of the equation：sin(x)-cos(x)=0
sin(x) - cos(x) = 0
sin(x) = cos(x)
- 2sin(π4 - x) = 0
x = π4+kπ , k ∈ Z