Since the result of the given sum is a constant, then the
value of th derivative of the sum must be zero.
We'll
assign a function to the given expression:
f(x) = arcsin
sqrt(1-x^2) + arccos x
We'll differentiate with respect to
x:
f'(x) = [sqrt(1-x^2)]'/sqrt(1 - 1 + x^2) - 1/sqrt(1 -
x^2)
f'(x) = -2x/2*|x|*sqrt(1-x^2) - 1/sqrt(1 -
x^2)
Since x is in the interval [-1 , 0] => |x| =
-x
f'(x) = -2x/-2x*sqrt(1-x^2) - 1/sqrt(1 -
x^2)
f'(x) = 1/sqrt(1 - x^2) - 1/sqrt(1 -
x^2)
f'(x) = 0
Since the 1st
derivative of f()x is cancelling out, then the function f(x) is a
constant.
Now, we'll check if the constant is
pi.
Let x = -1. We'll compute the value of f(x) for x
=-1.
f(-1) = arcsin sqrt(1 - 1) +
arccos(-1)
f(-1) = arcsin 0 +
arccos(-1)
f(-1) = 0 +
pi
f(-1) = pi
We'll replace x
by 0 and we'll get:
f(0) = arcsin sqrt(1 - 0) +
arccos(0)
f(0) = arcsin 1 + arccos
0
f(0) = pi/2 + pi/2
f(0) =
2pi/2
f(0) =
pi
The identity arcsin sqrt(1-x^2) + arccos x
= pi is verified for any value of x, over the range [-1 ,
0].
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