So 1 minus x squared. So there you have it. The derivative with respect to x of the inverse sine of x is equal to 1 over the square root of 1 minus x squared. So let me just make that very clear. If you were to take the derivative with respect to x of both sides of this, you would get dy dx is equal to this on the right-hand side. Or we could say the derivative with respect to x of the inverse sine of x is equal to 1 over the square root of 1 minus x squared. Now you could always reprove this if your memory starts to fail you, and actually that is the best way to really internalize this.