1.

In triangle $PQR$, $PQ$= 13 cm, $QR$= 6 cm and $RP$= 10 cm.  $QR$is produced to $S$.  

i) Find the value of cos $P\overset{\textasciicircum{}}{R}Q$, giving your answer as a fraction in its simplest form.

[3]

ii) Hence write down the value of cos $P\overset{\textasciicircum{}}{R}S$

[1]