What is the minimum value of function
f(x)=tanx+cotx
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Answers
Answer:
the minimum value of this function f(x) = tanx + cotx is 2.
Minimum Value of f(x)=tanx+cotx = 2
GIVEN: f(x)=tanx+cotx
TO FIND: Minimum Value.
SOLUTION:
As we know,
To find the minima or maxima value of f(x)
We need to put f(x) to be equal to 0.
Implying that,
f(x) = sec²x + (-cosec²x)
f(x) = 0 implies secx = ± cosecx
That means,
sinx=±cosx -------eq1
Also, we know,
x= Nπ ± π/4, N ∈ Z
Now,
We consider two values x= 45° and 135° each satisfying one of the equations in correspondence to eq1.
Therefore,
While putting x = 45
f(45°) = 1+1=2
And putting x = 135,
f(135°) = -1-1 =-2
Therefore the minimum value of f(x) is -2 where x is an integer.
Now,
Let tanx = y that implies cotx = 1/y
Also,
We know that the Arithmetic mean > the geometric mean.
Hence (y + 1/y)/2 is greater than or equal to √(y)*(1/y)
Implying that,
A minimum positive value of y+1/y ie. tanx + cotx is 2.
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