If the terminal point determined by $t$ is $P(a,b)$, then
(a) the terminal point $P(x,y)$ determined by $\pi-t$ is
$x=$ and $y=$ ;
(b) the terminal point $P(x,y)$ determined by $-t$ is
$x=$ and $y=$ ;
(c) the terminal point $P(x,y)$ determined by $\pi+t$ is
$x=$ and $y=$ ;
(d) the terminal point $P(x,y)$ determined by $2\pi+t$ is
$x=$ and $y=$ ;