Hello everyone I have a tangent line with slope =a=a to y=sinxy=sinx in 2 points (u1,v1),(u2,v2)(u1,v1),(u2,v2)
How can I prove that tana=atana=a?
My direction was to express aa with the points by a=u1−u2v1−v2a=u1−u2v1−v2
and the tangent line equation is y=ax−au1+v1y=ax−au1+v1
f(x)=sinx⟺f′(u)=cosuf(x)=sinx⟺f′(u)=cosu
so cosu1=acosu1=a and cosu2=acosu2=a?
