Trigonometric function is a kind of transcendental function in elementary function in mathematics. Their essence is the mapping between the set of arbitrary angles and a set of ratio variables. The usual trigonometric function is defined in the plane rectangular coordinate system, and its domain is the whole real number domain. The other is defined in a right triangle, but it is incomplete. Modern mathematics describes them as the limit of infinite sequence and the solution of differential equation, and extends their definitions to complex system. Because of the periodicity of trigonometric function, it does not have the inverse function in the sense of single-valued function. Trigonometric functions have important applications in complex numbers. Trigonometric function is also a common tool in physics. It has six basic functions: function name sine cosine tangent seccsc sine function sin(A)=a/h cosine function cos(A)=b/h tangent function tan(A)=a/b cotangent function cot(A)=b/ annex a: some special trigonometric function values sin0 = 0cos0 =1tan0 = 5 = (square root of 6 is 2)/4cos15 = (square root of 6+radical number 22 cos30= radical 3/2 tan30= radical 3/3 sin45= radical 2/2cos45 = sin45tan45 =1sin60 = cos30cos60 = Cos75 (self-comparison) Sin90=cos0 cos90=sin0 tan90 meaningless SIN/KOOC-0/05 = COS/KOOC-0/5 COS/KOOC-0/05 =-SIN/KOOC-0/5 TAN/KOOC-0/05 =-COT/KLOC. 120 =-TAN 60 SIN 135 = SIN 45 COS 135 =-COS 45 TAN 135 =-TAN 45 SIN 150 = SIN 30 COS 1 50 =-COS 30 TAN 150 =-TAN 30 SIN 165 = SIN 15 COS 65438

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