Are the rows of an orthogonal matrix A necessarily orthonormal?

Lecture 12: Deﬁnition of the Derivative (Sections 3.1) Tangent Lines and Slope Q y = f(x) P a x Def. The slope of the secant line through the point P(a,f(a)) and a nearby point Q(x,f(x)): Def. The tangent line to y = f(x)a ttheont P(a,f(a)) is the line through P with slope m = provided that the limit exists.