Composition of Inverse Trigonometric Functions and Trigonometric Functions
Let f 1 x =si...
Question
Let f1(x)=sin−1(cos(sin2x)),f2(x)=cos−1(sin(cos2x)),f3(x)=sin−1(cos(cos2x)) and f4(x)=cos−1(sin(sin2x)). Then which of the following is (are) CORRECT?
A
4∑i=1fi(x)=2π−2
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B
4∑i=1(−1)ifi(x)=0
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C
4∑i=1(−1)[i/3]fi(x)=0, where [.] denotes the greatest integer function
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D
f1(x)>f2(x)⇒cos2x>0
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Solution
The correct options are A4∑i=1fi(x)=2π−2 B4∑i=1(−1)ifi(x)=0 C4∑i=1(−1)[i/3]fi(x)=0, where [.] denotes the greatest integer function Df1(x)>f2(x)⇒cos2x>0 f1(x)=π2−sin2x f2(x)=π2−cos2x f3(x)=π2−cos2x f4(x)=π2−sin2x
f1(x)=f4(x) and f3(x)=f2(x) 4∑i=1fi(x)=f1(x)+f2(x)+f3(x)+f4(x) =2(π2−sin2x+π2−cos2x) =2(π−1)