So can we construct this in some way so this is a negative sine of x? Well what if I multiplied on the inside, what if I multiplied it by negative one? Well I can't just multiply it only one place by negative one I need to multiply by negative one twice so I'm not changing its value. So what if I said negative nine times negative sine of x? Well this is still gonna be nine sine of x. If you took negative nine times negative sine of x it is nine sine of x. And I did it this way because now negative sine of x it matches the derivative of cosine of x.