Hey Dany — ready when you are.
7. (i)
Step 1: Evaluate the function f(x) at x=0.
Given f(x)=3x3−x2+3x−1.
f(0)=3(0)3−(0)2+3(0)−1
f(0)=0−0+0−1
f(0)=−1
Step 2: Evaluate the function f(x) at x=1.
f(1)=3(1)3−(1)2+3(1)−1
f(1)=3−1+3−1
f(1)=4
Step 3: Apply the Intermediate Value Theorem.
Since f(x) is a polynomial, it is continuous for all real numbers. We found that f(0)=−1 (which is negative) and f(1)=4 (which is positive). Because f(0) and f(1) have opposite signs, by the Intermediate Value Theorem, there must be at least one root (a value of x where f(x)=0) between x=0 and x=1.
Thus, it is shown that the equation f(x)=0 has a root between 0 and 1.
7. (ii)
Step 1: Find dθdx and dθdy.
Given x=sin2θ and y=cos2θ.
dθdx=dθd(sin2θ)=2cos2θ
dθdy=dθd(cos2θ)=−2sin2θ
Step 2: Find dxdy using the chain rule.
dxdy=dx/dθdy/dθ=2cos2θ−2sin2θ
dxdy=−cos2θsin2θ=−tan2θ
Step 3: Find dx2d2y using the chain rule.
dx2d2y=dθd(dxdy)⋅dx/dθ1
First, find dθd(dxdy):
dθd(−tan2θ)=−sec2(2θ)⋅dθd(2θ)
=−sec2(2θ)⋅2
=−2sec2(2θ)
Now substitute this back into the formula for dx2d2y:
dx2d2y=(−2sec2(2θ))⋅2cos2θ1
dx2d2y=2cos2θ−2sec2(2θ)
Since sec2θ=cos2θ1:
dx2d2y=cos2(2θ)cos2θ−1
dx2d2y=cos3(2θ)−1
dx2d2y=−sec3(2θ)
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