cos(300) is equal to sin(?)
$$\small{
\cos{(300\ensurement{^{\circ}})} \text{ is equal to } \sin{(90\ensurement{^{\circ}}-300\ensurement{^{\circ}} )}
= \sin{(-210\ensurement{^{\circ}} )}
= \sin{(-210\ensurement{^{\circ}} + 360 \ensurement{^{\circ}} )}
=\sin{(150 \ensurement{^{\circ}} } )}
}$$