What would x be when y is pi over four? Well, to figure that out, we can go back to this original equation right over here. So when y is pi over four, you get, let me write it down, sine of x plus cosine of pi over four is equal to square root of two. Cosine of pi over four, we revert to our unit, or we think about our unit circle. We're in the first quadrant. If you think in degrees, it's a 45 degree angle. That's going to be square root of two over two.