The curve is .

The slope of the tangent line is .

Slope of the tangent is derivative of the curve.

So .

Consider . 

Differentiate on each side with respect to . 

Set slope = .

Substitute  in .

and

and

and

Imaginary values are not considered.

At , .

At , .

The points on the curve are  and .

The points on the curve are and .