[tex]\bf sin(\theta)=\cfrac{y}{r}
\qquad
% cosine
cos(\theta)=\cfrac{x}{r}\quad
\begin{cases}
r=radius=hypotenuse\\
x=adjacent\\
y=opposite\\
\theta=angle
\end{cases}\\
-----------------------------\\
thus
\\\\
\begin{cases}
r=4.5\\
\theta=45^o
\end{cases}\implies
\begin{cases}
sin(\theta)=\cfrac{y}{r}\to sin(45^o)=\cfrac{y}{4.5}\to 4.5\cdot sin(45^o)=y
\\\\
cos(\theta)=\cfrac{x}{r}\to cos(45^o)=\cfrac{x}{4.5}\to 4.5\cdot cos(45^o)=x
\end{cases}
\\\\
P\ is \ at\quad (x,y)[/tex]
the angle is in degrees, thus, when taking either sine or cosine, make sure your calculator is in Degree mode
