A) 0.48
B) 0.96
C) 0.6
D) None of these
Correct Answer: D
Solution :
Since, \[2{{\cos }^{-1}}x={{\cos }^{-1}}(2{{x}^{2}}-1)\] Therefore, \[2{{\cos }^{-1}}0.8={{\cos }^{-1}}(2\times 0.64-1)={{\cos }^{-1}}(0.28)\] \[\Rightarrow \] \[\cos (2{{\cos }^{-1}}0.8)=\cos ({{\cos }^{-1}}0.28)=0.28\]
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