Mathematics

Problem

For a curve described parametrically by

x=f(t),\;y=g(t)

with differentiable

f

and

g

, which one of the following conditions guarantees that the tangent at

t=t_{0}

is horizontal? a)

f'(t_{0})=g'(t_{0})

f'(t_{0})=0,\;g'(t_{0})\neq0

g'(t_{0})=0,\;f'(t_{0})\neq0

g'(t_{0})=0