Re: [csswg-drafts] [css-values-4] Normalization of arc trigonometric function values (#9625)

It's not about clamping. The sine is a periodic function, e.g. for any integer `n`, `sin(πn) = 0`.
The arcsine is the inverse function, so `asin(0)` must be one of these `πn`. We have to pick one, that's why CSS chooses the interval `[-90deg, 90deg]`, where we have a single solution. That is, `sin: [-π/2,  π/2] → [-1, 1] ` is bijective.

The image of the sine is the interval `[-1, 1]`, so `asin(2)` doesn't make sense, there is no number `x` such that `sin(x) = 2`. That's why CSS says to return NaN.

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Received on Thursday, 23 November 2023 21:33:05 UTC