For what value of k, is the function f(x)=⎧⎪
⎪⎨⎪
⎪⎩kcosxπ−2x, if x≠π23 if x=π2 continuous for all real x?
A
0
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B
π
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C
3
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D
6
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Solution
The correct option is D6 Since f(x) is continuous at x=π2 ∴f(π2)=limx→π2f(x)=limx→π2kcosxπ−2x→00 Apply L'hospital limx→π2−ksinx−2=3⇒limx→π2ksinx2=k2 k2=3⇒k=6