A curve C has equation
y = e^{2x} an x,
x ≠ (2n + 1) rac{ au}{2} - Edexcel - A-Level Maths Pure - Question 2 - 2008 - Paper 6
Question 2
A curve C has equation
y = e^{2x} an x,
x ≠ (2n + 1) rac{ au}{2}.
(a) Show that the turning points on C occur where tan x = -1.
(b) Find an equation of the ta... show full transcript
Worked Solution & Example Answer:A curve C has equation
y = e^{2x} an x,
x ≠ (2n + 1) rac{ au}{2} - Edexcel - A-Level Maths Pure - Question 2 - 2008 - Paper 6
Step 1
Show that the turning points on C occur where tan x = -1.
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Answer
To find the turning points of the curve C, we first differentiate the given equation.
Differentiate the function:
The derivative of y with respect to x is computed using the product rule:
dxdy=e2xtanx+e2xsec2x⋅dxdx
Therefore, we get:
dxdy=e2xtanx+2e2xsec2x.
Set the derivative to zero:
To find the turning points, we set the derivative to zero:
dxdy=0⇒2e2xtanx+e2xsec2x=0.
We can simplify this expression:
2tanx+1sec2x=0.
Solve the equation:
Rearranging gives:
2tanx+1=0⇒tanx=−1.
Hence, turning points occur when (\tan x = -1).
Step 2
Find an equation of the tangent to C at the point where x = 0.
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Answer
To find the equation of the tangent to the curve C at the point where x = 0, follow these steps:
Evaluate the derivative at x = 0:
Calculate (\frac{dy}{dx}) when (x = 0):
dxdyx=0=e0⋅tan(0)+2e0⋅sec2(0)=0+2⋅1=2.
Thus, the slope of the tangent line at (x = 0) is (2).
Determine the point on the curve:
Calculate y when (x = 0):
y=e0⋅tan(0)=1⋅0=0.
So, the point is (0, 0).
Use the point-slope form to write the tangent equation:
With point (0, 0) and slope 2, the equation is:
y−0=2(x−0)⇒y=2x.
Hence, the equation of the tangent line is (y = 2x).