`sin(u-v)=sin(u)cos(v)-cos(u)sin(v)`
`sin((9pi)/4-(5pi)/6)=sin((9pi)/4)cos((5pi)/6)-cos((9pi)/4)sin((5pi)/6)`
`sin((9pi)/4-(5pi)/6)=(sqrt2/2)(-sqrt3/2)-(sqrt2/2)(1/2)=-sqrt2/4(sqrt3+1)`
`cos(u-v)=cos(u)cos(v)+sin(u)sin(v)`
`cos((9pi)/4-(5pi)/6)=cos((9pi)/4)cos((5pi)/6)+sin((9pi)/4)sin((5pi)/6)`
`cos((9pi)/4-(5pi)/6)=(sqrt2/2)(-sqrt3/2)+(sqrt2/2)(1/2)=-sqrt2/4(sqrt3-1)`
`tan(u-v)=(tan(u)-tan(v))/(1+tan(u)tan(v))`
`tan((9pi)/4-(5pi)/6)=(1-(-sqrt3/3))/(1+(1)(-sqrt3/3))=((3+sqrt3)/3)/((3-sqrt3)/3)=(3+sqrt3)/(3-sqrt3)`
After rationalizing the denominator the answer is `2+sqrt3.`
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