Write the principal value of `cos^(-1)(cos680^0)dot`

1.	Write the principal value of `cos^(-1)(cos680^0)dot`
Answer» `cos^-1(cos 680^@) ` As, `680= 360 + 320` so, `cos^-1[cos(360+320)]` `cos^-1 [ cos(360 - 40)] ` `cos^-1[cos(40)]` `cos^-1[cos(40 xx pi/100)]` `cos^-1[cos((2pi)/9)]` `(2pi)/9` Answer

Discussion

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