Let be the greatest and be the least value of , then find the value of
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Taking the first derivative equal to zero yields:
f ′ ( x ) = 2 1 − x 2 1 ⋅ [ arcsin ( x ) 1 − arccos ( x ) 1 ] = 0 ;
or arcsin ( x ) = arccos ( x ) ⇒ arcsin ( x ) = arcsin ( 1 − x 2 ) ⇒ x = 1 − x 2 ⇒ 2 x 2 = 1 ⇒ x = 2 1
The second derivative at x = 2 1 yields:
f ′ ′ ( 1 / 2 ) = − π 3 / 2 8 < 0 (a maximum). Hence, M = π / 4 + π / 4 = 2 ⋅ π / 2 = π .
The minimum value, m , occurs when arcsin ( x ) = 1 , arccos ( x ) = 0 ⇒ x = 1 , or π / 2 + 0 = π / 2 . Finally, ( m M ) 2 = ( π / ( π / 2 ) ) 2 = ( 2 ) 2 = 2 .