[tex] \bf \textit{Cofunction Identities}
\\\\
sin\left(90^o-\theta\right)=cos(\theta)
\qquad
cos\left(90^o-\theta\right)=sin(\theta)\\\\
-------------------------------\\\\
sin(x)=cos(\stackrel{90^o-x}{54^o})\implies 90^o-x=54^o
\\\\\\
90^o-54^o=x\implies 36^o=x [/tex]