Respuesta :
[tex]\bf \textit{Cofunction Identities}
\\ \quad \\
\boxed{sin\left(\frac{\pi}{2}-{{ \theta}}\right)=cos({{ \theta}})}\qquad
cos\left(\frac{\pi}{2}-{{ \theta}}\right)=sin({{ \theta}})
\\ \quad \\ \quad \\
tan\left(\frac{\pi}{2}-{{ \theta}}\right)=cot({{ \theta}})\qquad
cot\left(\frac{\pi}{2}-{{ \theta}}\right)=tan({{ \theta}})
\\ \quad \\ \quad \\
sec\left(\frac{\pi}{2}-{{ \theta}}\right)=csc({{ \theta}})\qquad
csc\left(\frac{\pi}{2}-{{ \theta}}\right)=sec({{ \theta}})\\\\
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[tex]\bf \begin{array}{lcllclll} sin(&90^o-\theta)&=&cos(&\theta)\\ &\uparrow &&&\uparrow \\ &3x+15&&&7x-2\\ &\downarrow \\ &90-(7x-2) \end{array} \\\\\\ 90-(7x-2)=3x+15\implies 90-7x+2=3x+15 \\\\\\ 92-15=10x\implies 77=10x\implies \cfrac{77}{10}=x[/tex]
[tex]\bf \begin{array}{lcllclll} sin(&90^o-\theta)&=&cos(&\theta)\\ &\uparrow &&&\uparrow \\ &3x+15&&&7x-2\\ &\downarrow \\ &90-(7x-2) \end{array} \\\\\\ 90-(7x-2)=3x+15\implies 90-7x+2=3x+15 \\\\\\ 92-15=10x\implies 77=10x\implies \cfrac{77}{10}=x[/tex]