Recall the cofunction identity:[br][math]\cos x=\sin\left(\frac{\pi}{2}-x\right)[/math][br]We can use this to relate the graphs of sine and cosine.[br]Starting with[br][list=1][*][math]f\left(x\right)=\sin x[/math] [i]Check the box next to Sine to see a portion of the sine curve.[/i][/*][*][math]f\left(-x\right)=\sin\left(-x\right)[/math] (Reflection across the y-axi) [i][size=85]Use the slider to show it[/size][/i][/*][*][math]f\left(-\left(x-\frac{\pi}{2}\right)\right)=f\left(\frac{\pi}{2}-x\right)=\sin\left(\frac{\pi}{2}-x\right)[/math] (Translation right [math]\frac{\pi}{2}[/math] units) [i][size=85]Use the slider[/size][/i][/*][/list][br][size=100]We can see that the final outcome is the same as the cosine curve (check by switching it on).[/size]