Write the equation of the tangent line to the cure y=cosx at a=pi/4(adsbygoogle = window.adsbygoogle || []).push({});

(y-y1)=m(x-x1)

cos(pi/4)=sqrt(2)/2

y'=-sinx=-sin(pi/4)=-sqrt(2)/2

(y-sqrt(2)/2)=m(x-pi/4)

y'=-sqrt(2)/2(x-pi/4)+sqrt(2)/2

My teacher circled they'and took a point off. I know that y'=-sinx but what should be in its place?

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# Homework Help: Tangent line

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