How is sine of 90 degree possible

I don't know how can a triangle be formed with two angles each 90 degree. If it is not possible, then how do we calculate sin 90 degree = 1 ?

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sin 90 Degrees Equals 1 Why?

Why does sin 90 degrees equal 1? We know that formula for sin is perpendicular upon hypotenuse where hypotenuse is longest side? - EduRev Class 10 Question

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Sin 90 Degrees Value, Calculation, Periodicity & Examples

Replying to @user9875741336510 why #sine of 90° = 1 #mathematics #math, Math

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Solved iii. Using the definition given above, what are