"Induction formula memory formulas"
for K?π/2±α (k∈z), the transition between trigonometric functions is:
① when K is even, the function value of α is obtained, that is, the function name does not change;
② when k is odd, the corresponding residual function value of α is obtained, i.e. Sin→cos;cos→sin;tan→cot,cot→tan.odd Change even unchanged)
It is
then preceded by a sign of the value of the original function when α is considered a sharp angle . (symbol See quadrant)
Formula One:
set α to an arbitrary angle, with the same trigonometric function values equal to the same angle of the end edge:
sin (2kπ+α) =sinα
cos (2kπ+α) =cosα
Tan (2kπ+α) =tanα
Cot (2kπ+α) =cotα
Formula Two:
The relationship between the trigonometric function value of π+α and the trigonometric function value of α is set to α as an arbitrary angle:
sin (π+α) =-sinα
cos (π+α) =-cosα
Tan (π+α) =tanα
Cot (π+α) =cotα
Formula Three:
relationship between the trigonometric function values of arbitrary angular α and-α:
sin (-α) =-sinα
cos (-α) =cosα
Tan (-α) =-tanα
Cot (-α) =-cotα
Formula Four:
the relationship between the trigonometric function values of π-α and α can be obtained by using Formula Two and Formula Three:
sin (π-α) =sinα
cos (π-α) =-cosα
Tan (π-α) =-tanα
Cot (π-α) =-cotα
Formula Five:
the relationship between the trigonometric function values of 2π-α and α can be obtained by using Formula One and Formula Three:
sin (2π-α) =-sinα
cos (2π-α) =cosα
Tan (2π-α) =-tanα
Cot (2π-α) =-cotα
Formula Six:
the relationship between Π/2±α and the trigonometric function values of α:
sin (π/2+α) =cosα
cos (π/2+α) =-sinα
Tan (π/2+α) =-cotα
Cot (π/2+α) =-tanα
sin (π/2-α) =cosα
cos (π/2-α) =sinα
Tan (π/2-α) =cotα
Cot (π/2-α) =tanα
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The conversion formula between trigonometric functions
