Animated Solution for Mathematics - Functions: The domain of the function f(x)=loge(x2−3x+2)cos−1(x2−9x2−5x+6) is
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Visualized Solution
Identifying Domain Constraints
Function: f(x)=loge(x2−3x+2)cos−1(x2−9x2−5x+6)
Constraint 1: Argument of cos−1(u) must be in [−1,1].
Constraint 2: Argument of loge(v) must be v>0.
Constraint 3: Denominator cannot be zero, so loge(v)=0⇒v=1.
Simplifying the Numerator Argument
Let u=x2−9x2−5x+6
Factorizing: u=(x−3)(x+3)(x−2)(x−3)
For x=3 and x=−3, u=x+3x−2
Solving the Right Inequality: u≤1
We need x+3x−2≤1
Rearranging: x+3x−2−1≤0
Simplifying: x+3−5≤0
Since numerator is negative, denominator must be positive: x+3>0⇒x>−3
Solving the Left Inequality: u≥−1
We need x+3x−2≥−1
Rearranging: x+3x−2+1≥0
Simplifying: x+32x+1≥0
Critical points: x=−3,x=−21
Using wavy curve method: x∈(−∞,−3)∪[−21,∞)
Combining Numerator Conditions
From u≤1: x>−3
From u≥−1: x∈(−∞,−3)∪[−21,∞)
Intersection gives: x∈[−21,∞)
Also x=3 from original denominator.
Denominator Constraint: Log Argument
For loge(x2−3x+2) to be defined, x2−3x+2>0
Factorizing: (x−1)(x−2)>0
Critical points: x=1,x=2
Solution: x∈(−∞,1)∪(2,∞)
Denominator Constraint: Non-Zero Check
The denominator cannot be zero: loge(x2−3x+2)=0
This means the argument cannot be 1: x2−3x+2=1
Simplifying: x2−3x+1=0
Finding the Excluded Roots
Solving x2−3x+1=0 using quadratic formula:
x=23±9−4=23±5
Approximate values: 0.382 and 2.618
These points must be excluded from the domain.
The Final Intersection
Numerator: x∈[−21,∞)∖{3}
Denominator: x∈(−∞,1)∪(2,∞)
Excluded: x=23±5
Intersecting all gives the final valid regions.
The JEE Trap & Final Answer
Technically, x=3 should be excluded.
However, looking at the given options, x=3 is not explicitly removed.
In such cases, choose the most accurate available option.
Final Answer: [−21,1)∪(2,∞)−{23+5,23−5}
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The Sigma Insight: Domain and Range of a Function
Solution Diagram
Analyzing the Setup
To find the domain of the function f(x)=loge(x2−3x+2)cos−1(x2−9x2−5x+6), we must satisfy three primary mathematical constraints:
1. The argument of the inverse cosine function must lie in the interval [−1,1].
2. The argument of the logarithm must be strictly positive.
3. The denominator must not equal zero, meaning the logarithm cannot be zero.
Solving the Numerator Constraint
The argument of the inverse cosine is g(x)=x2−9x2−5x+6. Factoring the expression, we get:
g(x)=(x+3)(x−3)(x−2)(x−3)
We must immediately note that $x
eq 3$ and $x
eq -3$ to avoid division by zero. Simplifying the expression for $x
eq 3$, we obtain g(x)=x+3x−2.
We require −1≤x+3x−2≤1. Solving x+3x−2≤1:
x+3x−2−1≤0⇒x+3x−2−x−3≤0⇒x+3−5≤0
This inequality holds when x+3>0, or x>−3.
Solving x+3x−2≥−1:
x+3x−2+1≥0⇒x+3x−2+x+3≥0⇒x+32x+1≥0
Using the Wavy Curve Method with critical points x=−3 and x=−1/2, the solution is x∈(−∞,−3)∪[−1/2,∞). Intersecting these conditions, the numerator is valid for x∈[−1/2,∞)∖{3}.
Solving the Denominator Constraint
The logarithm loge(x2−3x+2) requires x2−3x+2>0. Factoring gives (x−1)(x−2)>0, which implies x∈(−∞,1)∪(2,∞).
Additionally, the denominator cannot be zero, so $\log_e(x^2-3x+2)
eq 0$. This implies:
x2−3x+2eq1⇒x2−3x+1eq0
Using the quadratic formula, we find the roots to be x=23±5. These values must be excluded from the domain.
Final Calculation
We intersect the valid regions:
1. Numerator: x∈[−1/2,∞)∖{3}
2. Denominator: x∈(−∞,1)∪(2,∞)
3. Exclusions: $x
eq \frac{3 \pm \sqrt{5}}{2}$
The intersection of the numerator and denominator regions is [−21,1)∪(2,3)∪(3,∞). Removing the points 23−5≈0.38 and 23+5≈2.62, we arrive at the final domain: