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Here are the solutions to the problems:
3. (i) Draw the truth table for each of the propositions p⟹q and ∼p∨q and show that they are identical.
Step 1: Create a truth table for p and q.
Step 2: Determine the truth values for p⟹q.
Step 3: Determine the truth values for ∼p.
Step 4: Determine the truth values for ∼p∨q.
Step 5: Compare the columns for p⟹q and ∼p∨q.
pTTFFqTFTFp⟹qTFTT∼pFFTT∼p∨qTFTT
The columns for p⟹q and ∼p∨q are identical, which shows that the two propositions are equivalent.
3. (ii) Given that sin−1(x)=α and cos−1(x)=β, show that sin(α+β)=1.
Step 1: Use the property of inverse trigonometric functions.
We know that for any x∈[−1,1], the sum of sin−1(x) and cos−1(x) is 2π.
Step 2: Substitute the given values into the identity.
Given sin−1(x)=α and cos−1(x)=β, we have:
α+β=2π
Step 3: Calculate sin(α+β).
sin(α+β)=sin(2π)
Step 4: Evaluate the sine function.
sin(2π)=1
Thus, sin(α+β)=1.
4. (i) The function f is given by f(x)=(x−1)(x2+1)x+1. Express f(x) in partial fractions. Hence find ∫f(x)dx.
Part 1: Partial Fractions
Step 1: Set up the partial fraction decomposition.
(x−1)(x2+1)x+1=x−1A+x2+1Bx+C
Step 2: Multiply by the common denominator (x−1)(x2+1).
x+1=A(x2+1)+(Bx+C)(x−1)
Step 3: Solve for A, B, and C.
Substitute x=1:
1+1=A(12+1)+(B(1)+C)(1−1)
2=2A⟹A=1
Expand the equation:
x+1=Ax2+A+Bx2−Bx+Cx−C
x+1=(A+B)x2+(−B+C)x+(A−C)
Equate coefficients:
Coefficient of x2: 0=A+B⟹0=1+B⟹B=−1
Coefficient of x: 1=−B+C⟹1=−(−1)+C⟹1=1+C⟹C=0
Constant term: 1=A−C⟹1=1−0⟹1=1 (consistent)
Step 4: Write the partial fraction decomposition.
f(x)=x−11+x2+1−x+0=x−11−x2+1x
Part 2: Integration
Step 5: Integrate each term.
∫f(x)dx=∫(x−11−x2+1x)dx
∫x−11dx−∫x2+1xdx
The first integral is ln∣x−1∣.
For the second integral, let u=x2+1, then du=2xdx, so xdx=21du.
∫x2+1xdx=∫u1⋅21du=21∫u1du=21ln∣u∣+C=21ln(x2+1)+C
Step 6: Combine the results.
∫f(x)dx=ln∣x−1∣−21ln(x2+1)+C
The final answer is ln∣x−1∣−21ln(x2+1)+C.
4. (ii) By using the substitution u=sinx, find ∫(1+sin2xcosx)dx.
Step 1: Define the substitution.
Let u=sinx.
Step 2: Find du.
Differentiating u with respect to x gives du=cosxdx.
Step 3: Substitute u and du into the integral.
∫1+sin2xcosxdx=∫1+u21du
Step 4: Evaluate the resulting integral.
This is a standard integral:
∫1+u21du=arctan(u)+C
Step 5: Substitute back u=sinx.
arctan(sinx)+C
The final answer is arctan(sinx)+C.
4. (iii) Find ∫(x+2)e3xdx.
Step 1: Use integration by parts, ∫udv=uv−∫vdu.
Step 2: Choose u and dv.
Let u=x+2 and dv=e3xdx.
Step 3: Find du and v.
Differentiate u: du=1dx.
Integrate dv: v=∫e3xdx=31e3x.
Step 4: Apply the integration by parts formula.
∫(x+2)e3xdx=(x+2)(31e3x)−∫(31e3x)(1)dx
=31(x+2)e3x−31∫e3xdx
Step 5: Evaluate the remaining integral.
31(x+2)e3x−31(31e3x)+C
Step 6: Simplify the expression.
=31(x+2)e3x−91e3x+C
You can also factor out e3x:
=e3x(31(x+2)−91)+C
=e3x(93(x+2)−1)+C
=e3x(93x+6−1)+C
=9e3x(3x+5)+C
The final answer is 9e3x(3x+5)+C.
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