We have `|{:("sin"10^(@), -"cos"10^(@)), ("sin"80^(@), "cos"80^(@)):}|`
`=("sin"10^(@))("cos" 80^(@)) - ("sin" 80^(@))(-"cos" 10^(@))`
`= ("sin" 10^(@) "cos" 80^(@) + "cos" 10^(@) "sin"80^(@))`
`= "sin" (10^(@) +80^(@)) " "[because "sin" A"cos" B + "cos" A"sin" B = "sin (A+B)]`
`="sin" 90^(@) =1.`
