Write $cos{(pi-:4)-a}$ in terms of trigonometric ratios of just $a$ ?

Question

1845 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2017-10-02T07:33:48

$cos{(pi-:4)-a}=1/sqrt2(cosa+sina)$

As $Cos(A-B)=cosAcosB+sinAsinB$

$cos{(pi-:4)-a}=cos(pi/4-a)$

= $cos(pi/4)cosa+sin(pi/4)sina$

= $1/sqrt2cosa+1/sqrt2sina$

= $1/sqrt2(cosa+sina)$

Write cos{(pi-:4)-a}cos{(pi-:4)-a} in terms of trigonometric ratios of just aa?