Answer process:

Using the definition of trigonometric function of any angle, it can be deduced that when the vertex of angle 90 is at the origin and the starting edge coincides with the positive semi-axis of X axis, it is easy to know that the final edge of the angle is on the positive semi-axis of Y axis. If a point on the final edge is p (0, 1), the distance from point P to the origin is r= 1.

From the definition of trigonometric function from any angle, we can get: sin90 = y/r =1=1,COS90 = x/r = 0/ 1 = 0, TAN90 = y/x? Meaningless, COT 90 = X/Y = 0/ 1 = 0.

Extended data:

I. Related inductive formulas

cot(kπ+α)=cot α

cot(π/2-α)=tan α

cot(π/2+α)=-tan α

Kurt (-α) =-Kurt α

cot(π+α)=cot α

Kurt (π-α) =-Kurt α

Second, the function formula

1, product and difference formula

sinαcosβ=( 1/2)*[sin(α+β)+sin(α-β)]

cosαsinβ=( 1/2)*[sin(α+β)-sin(α-β)]

cosαcosβ=( 1/2)*[cos(α+β)+cos(α-β)]

2. Sum-difference product formula

sinα+sinβ= 2 * sin[(α+β)/2]* cos[(α-β)/2]

sinα-sinβ= 2 * cos[(α+β)/2]* sin[(α-β)/2]

cosα+cosβ= 2 * cos[(α+β)/2]* cos[(α-β)/2]

cosα-cosβ=-2 * sin[(α+β)/2]* sin[(α-β)/2]

3. Sum and difference of two angles

sin(α+β)=sinαcosβ+cosαsinβ

sin(α-β)=sinαcosβ-cosαsinβ

cos(α+β)=cosαcosβ-sinαsinβ

cos(α-β)=cosαcosβ+sinαsinβ

tan(α+β)= =(tanα+tanβ)/( 1-tanαtanβ)

tan(α-β)=(tanα-tanβ)/( 1+tanαtanβ)

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