Question

cos inverse (1/√5)+cos inverse (2/√5)= π/2

Answer 1

It's an identity!

${cos}^{ - 1} (x) + {cos}^{ - 1} (y) = \pi \div 2 \: \: \: \\ if \: {x}^{2} + {y}^{2} = 1$

Answer 2

Answer:

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