1305 is a measurement larger than 360, so keep subtracting 360 till you get a number smaller than 360, or divide by 360 to find the remainder
the number is 225
225 degree on a unit circle is in the 3rd quadrant, with the terminal line forming a 45 degree angle with the negative x axis. the y value is -√2/2, the hypotenuse is 1, so sin1305=(-√2)/2
