You're on a roll —
Step 1: Understand the principal values of inverse trigonometric functions.
For sec−1x, the principal value range is [0,π]−{2π}.
For csc−1x, the principal value range is [−2π,2π]−{0}.
The domain for both sec−1x and csc−1x is x∈(−∞,−1]∪[1,∞).
Step 2: Define the function f(x) and its range.
Let A=sec−1x and B=csc−1x.
The function given is f(x)=16(sec−1x)2+(csc−1x)2.
We know the identity sec−1x+csc−1x=2π for x∈(−∞,−1]∪[1,∞).
So, B=2π−A.
Substitute this into the function:
f(x)=16A2+(2π−A)2
The range of A=sec−1x is [0,π]−{2π}.
Step 3: Find the maximum and minimum values of f(x).
Let g(A)=16A2+(2π−A)2.
Expand the expression:
g(A)=16A2+4π2−πA+A2
g(A)=17A2−πA+4π2
This is a quadratic function of A, opening upwards (since the coefficient of A2 is positive). Its vertex occurs at A=−2(17)−π=34π.
The value 34π is within the range [0,π]−{2π}.
The minimum value of g(A) occurs at the vertex:
g(34π)=17(34π)2−π(34π)+4π2
g(34π)=17342π2−34π2+4π2
g(34π)=2×34π2−34π2+4π2
g(34π)=68π2−682π2+6817π2
g(34π)=681−2+17π2=6816π2=174π2
This is the minimum value.
To find the maximum value, we need to evaluate g(A) at the endpoints of the interval for A, which are 0 and π. We also need to consider the behavior around 2π, but since it's a quadratic opening upwards, the maximum will be at the endpoints.
At A=0:
g(0)=17(0)2−π(0)+4π2=4π2
At A=π:
g(π)=17π2−π(π)+4π2=17π2−π2+4π2=16π2+4π2=464π2+π2=465π2
Comparing 4π2 and 465π2, the maximum value is 465π2.
Step 4: Calculate the sum of the maximum and minimum values.
Sum = Maximum value + Minimum value
Sum=465π2+174π2
To add these fractions, find a common denominator, which is 4×17=68.
Sum=4×1765π2×17+17×44π2×4
Sum=681105π2+6816π2
Sum=681105π2+16π2=681121π2
Let's recheck the question. It asks for the sum of the maximum and minimum values of 16(sec−1x)2+(csc−1x)2.
Let's re-evaluate the range of A=sec−1x.
The range of sec−1x is A∈[0,π] excluding A=2π.
The function is g(A)=17A2−πA+4π2.
The minimum value is g(34π)=174π2.
The maximum value will occur at the boundary points of the interval [0,π].
g(0)=4π2
g(π)=17π2−π2+4π2=16π2+4π2=465π2.
The maximum value is 465π2.
The sum of the maximum and minimum values is 465π2+174π2=681105π2+16π2=681121π2.
This value is approximately 681121×(3.14159)2≈681121×9.8696≈6811060≈162.6π2.
The given options are 18π2, 31π2, 24π2, 22π2. None of these match 681121π2.
Let's re-examine the problem statement and my understanding.
"Using the principal values of the inverse trigonometric functions, the sum of the maximum and the minimum values of 16(sec−1x)2+(csc−1x)2 is"
Could there be a mistake in the identity or the range?
The identity sec−1x+csc−1x=2π is correct for x∈(−∞,−1]∪[1,∞).
The principal range for sec−1x is [0,π]−{2π}.
The principal range for csc−1x is [−2π,2π]−{0}.
Let A=sec−1x. Then A∈[0,π] and A=2π.
Let B=csc−1x. Then B∈[−2π,2π] and B=0.
From A+B=2π, we have B=2π−A.
If A=0, then B=2π. This is valid.
If A=π, then B=−2π. This is valid.
If A=2π, then B=0. This is not allowed for csc−1x. So A=2π.
The function is g(A)=17A2−πA+4π2.
The minimum value is g(34π)=174π2.
The maximum value is at the endpoints of the interval for A.
The interval for A is [0,π] excluding 2π.
The function g(A) is continuous on [0,π].
The maximum value of a continuous function on a closed interval occurs at the endpoints or critical points.
The critical point is A=34π, which gives the minimum.
The endpoints are A=0 and A=π.
g(0)=4π2.
g(π)=465π2.
The maximum value is 465π2.
The sum is 681121π2.
Let's check if there's any other interpretation of the problem.
Perhaps the question implies that x must be such that both sec−1x and csc−1x are defined. This is already handled by the identity.
Could there be a typo in the question or options?
Let's assume the question meant 16(sec−1x)2+(sec−1x)2=17(sec−1x)2.
Then the range of A=sec−1x is [0,π] excluding 2π.
The minimum value would be 17(0)2=0.
The maximum value would be 17(π)2=17π2.
Sum = 0+17π2=17π2. This is close to 18π2 (option 1). But this is not the function given.
Let's assume the question meant 16(csc−1x)2+(csc−1x)2=17(csc−1x)2.
The range of B=csc−1x is [−2π,2π] excluding 0.
The minimum value of 17B2 would be 17(0)2=0 (but B=0, so it approaches 0).
The maximum value would be 17(2π)2=417π2.
Sum = 0+417π2=417π2=4.25π2. This is not among the options.
Let's re-check the calculation of the sum.
Min value: 174π2≈0.235π2
Max value: 465π2=16.25π2
Sum: 681121π2≈16.485π2.
This is not close to any of the options 18π2,31π2,24π2,22π2.
Let's consider if the problem implies x is restricted to a specific range, e.g., x≥1 or x≤−1.
If x≥1, then sec−1x∈[0,2π).
If x≤−1, then sec−1x∈(2π,π].
The problem states "principal values", so the full range [0,π]−{2π} should be used.
Let's re-evaluate the function g(A)=17A2−πA+4π2 over the two intervals for A: [0,2π) and (2π,π].
The vertex A=34π is in the interval [0,2π).
So the minimum value is indeed g(34π)=174π2.
For the maximum value:
On [0,2π): The function is increasing from A=34π to A=2π.
The value approaches g(2π)=17(2π)2−π(2π)+4π2=417π2−2π2+4π2=417π2−2π2+π2=416π2=4π2.
On (2π,π]: The function is increasing from A=2π to A=π.
The value at A=π is g(π)=465π2.
So the maximum value is 465π2.
The sum remains 681121π2.
Let's consider a common mistake or a different interpretation of the problem.
What if the question meant 16(sec−1x)2+(2π−sec−1x)2 and the range of sec−1x was restricted to [0,2π] or [−2π,0]?
But the principal value range for sec−1x is [0,π]−{2π}.
Let's check the options again.
(1) 18π2
(2) 31π2
(3) 24π2
(4) 22π2
My calculated sum is ≈16.485π2.
This is closest to 18π2.
Is it possible that the minimum value is 0?
If A=0, g(0)=4π2.
If A=2π (not allowed), g(2π)=4π2.
If A=π, g(π)=465π2.
Let's consider the possibility that the question is simpler and involves a different identity or range.
For example, if the range of sec−1x was [0,2π] and csc−1x was [0,2π]. This is not standard.
Let's assume there is a typo in the question and it was 16(sec−1x)2+(sec−1x)2=17(sec−1x)2.
Then A∈[0,π]−{2π}.
Min value is 17×02=0.
Max value is 17×π2=17π2.
Sum = 17π2. This is very close to 18π2.
Let's consider another possibility.
What if the question meant 16(sec−1x)2+(csc−1x)2 and the range of sec−1x was restricted to A∈[0,2π) and A∈(2π,π]?
The minimum value is 174π2.
The maximum value is 465π2.
The sum is 681121π2.
Let's try to find an integer multiple of π2 as an answer.
If the minimum value was 0, then the sum would be $\frac