Cos85° *cos40°-sin85°*sin(-40°) --------------------------------- = Sin40°*cos5°+cos40°*sin5°

[latex] frac{cos85cos40+sin85sin40}{sin40cos5+cos40sin5}= frac{cos(85-40)}{sin(40+5)}= frac{cos45}{sin45}=ctg45=1 [/latex]

cos85⁰*cos40⁰ - sin85⁰*sin(-40⁰) = cos85⁰*cos40⁰ + sin85⁰*sin40 = cos(85-40) = cos 45⁰ = [latex] frac{ sqrt{2} }{2} [/latex]sin40⁰*cos5⁰+cos40⁰sin5⁰ = sin (40+5) = sin 45⁰ = [latex] frac{ sqrt{2} }{2} [/latex][latex] frac{ sqrt{2} }{2} : frac{ sqrt{2} }{2} = 1[/latex]