A2 Mathematics: C4 Core Maths   Curves and TangentsParametric Curves
ObjectivesWe will be able to Plot Graphs defined by parametric equationsby hand and by calculatorUse algebra to eliminate the parameter and find the Cartesian equation of the curve.Find the gradient of the curve for any value of the parameter.Find the equation of the tangent or normal to the curve at any value of the parameter.
What is a Parametric Graph ? To plot a graphwe could follow a point as it crawls along the curveespeciallyIf the point obeys a ruleIf it gives x and yIn terms of time Or other parameter
Tracing out a Parametric Graph http://www.flashandmath.com/mathlets/calc/param2d/param_advanced.html
Tracing out a Parametric Graph This also shown in your WEC text-bookOn page 323
Parametric Curve examples
Parametric Curve examples
Parametric Curve examples
 Parametric Equations for a Curvex=2t, y=15t– 5t²
Plotting x and y via parameters
 Curves defined by parametric equations
 Parametric Equations for a Curvex = 3cosθ, y = 3sinθ
Plotting x and y via parameters
 Curves defined by parametric equations
Plotting Parametric CurvesUse Sharp EL9900 calculatorParametric settings on next slideUse AutographEquation entry via x=2t, y=t^2Separated by a comma
 Parametric Settings for EL9900
 Parametric Entry for EL9900
 Parametric Displays on the EL9900
Cartesian Equation for a CurveWe have x 	as a function of t or θ	Andyas a function of t or θWe need to eliminate t or θLeaving only x and y.MethodsEliminate t by substitution and algebraEliminate θ via trigonometric Identities and algebra
Cartesian Equation – Eliminate tx = t2,   y = t – t2
Cartesian Equation – identities in θx = 3cosθ,   y = sinθ
Activity step 1Use table of values to plot each curve (and/or use your calculator).Match each parameter formula and its curve with correct curve card.Match each curves with its correct Cartesian equation.
 Parametric Equations for a Curvex = 3cosθ, y = 3sinθ
 Cartesian Equation for a Curvex2 + y2 = 9
 Curves defined by parametric equations
 Parametric Equations for a Curvex=2t, y=15t– 5t²
 Cartesian Equation for a Curve4y = 15x– 4.9x2
 Curves defined by parametric equations
 Parametric Equations for a Curve  x=t²–4,   y=t³–4t
 Cartesian Equation for a Curvey = x√(x+4) y = x(x+4)0.5
 Curves defined by parametric equations
 Parametric Equations for a Curvex=sinθ,    y=sin2θ
 Cartesian Equation for a Curvey = 2x√(1-x2)y = 2x(1-x2)0.5
 Curves defined by parametric equations
 Parametric Equations for a Curvex=t2,    y=t3
 Cartesian Equation for a Curvey=x√x
 Curves defined by parametric equations
 Parametric Equations for a Curvex=t,    y=1/t
 Cartesian Equation for a Curve    y = 1/x
 Curves defined by parametric equations
 Parametric Equations for a Curvex = 1+ t,  y = 2 - t
 Cartesian Equation for a Curvex + y = 3
 Curves defined by parametric equations
 Parametric Equations for a Curvex=(2+3t)/(1+t),  y=(3–2t)/(1+t)
 Parametric Equations for a Curve   y=13–5x
 Curves defined by parametric equationsStops here !
Extension: Try these Parametersx= t + 1/t,  y= t - 1/tx = 3cosθ, y= sinθInvestigate/Create your own
 Parametric Equations for a Curvex=………....,  y=…….……..
 Curves defined by parametric equations
Tangents to the curve?How do we find dy/dx ?How do we find the equation of the tangent at one particular point on the curve – for example when t=1
 Parametric Equations for a Curvex = 3cosθ, y = 3sinθ
 Gradient of Tangents to the CurveWe know (why?) that
 Gradient of Tangents to the Curvex = 3cosθ,       	y = 3sinθ...so.....
 Gradient of Tangents to the CurvePutting it together.......
How do we find a particular tangent?Given a particular t value  find x and y, and dy/dxNow we have the gradient of the tangent and
the co-ordinates where it touches the curve.......so.....
 Equation of  one Tangent to Circle
 Equation of  one Tangent to Circle  x = 3cosπ/4,       	y = 3sin π/4    ...so.....
Image of one Tangent to the Curve
Activity step 2Use x and y parameter functions, to match dy/dx equation   one tangent equation with previous cards
 Parametric Equations for a Curvex=2t, y=15t– 5t²
 Gradient of Tangents to the Curve
 Image of one Tangent to the Curve
 Equation of one Tangent to the Curve
 Parametric Equations for a Curve  x=t²–4,   y=t³–4t
Gradient of Tangents to the Curve
Image of  one Tangent to the Curve
Equation of One Tangent to the Curve
 Parametric Equations for a Curvex=sinθ,    y=sin2θ
Gradient of Tangents to the Curve
Image of Tangent to Curve
Equation of One Tangent to the Curve
 Parametric Equations for a Curvex=t2,    y=t3
 Gradient of Tangents to the Curve
 Image of Tangent to Curve
 Equation of one Tangent to the Curve
 Parametric Equations for a Curvex=t,    y=1/t
 Gradient of Tangents to the Curve
 Image of Tangent to Curve
 Equation of one Tangent to the Curve
 Parametric Equations for a Curvex = 1+ t,  y = 2 - t
Gradient of Tangents to the Curve
 Image of Tangent to Curve
 Equation of one Tangent to the Curve
 Parametric Equations for a Curvex=(2+3t)/(1+t),  y=(3–2t)/(1+t)
Gradient of Tangents to the Curve
Image of Tangent to Curve
 Equation of one Tangent to the Curve
 Parametric Equations for a Curvex=………....,  y=…….……..
 Curves defined by parametric equations
Gradient of Tangents to the Curve
 Equation of one Tangent to the Curve
Image of Tangent to Curve

C4 parametric curves_lesson