[" 8.Prove that "],[[" (i) "cos15^(@)-sin15^(@)=(1)/(sqrt(2))],[" (ii) "cot105^(@)-tan105^(@)=2sqrt(3)],[" (iii) "(tan69^(@)+tan66^(@))/(1-tan69^(@)tan66^(@))=-1]]

Prove that (tan69^(@)+tan66^(@))/(1-tan69^(@)tan66^(@))=-1

Prove that (i) "cos " 15^(@) - " sin " 15^(@) = (1)/(sqrt(2)) (ii) " cot " 105^(@) - " tan " 105^(@) =2sqrt(3) (iii) (tan 69^(@) + tan 66^(@))/(1-tan 69^(@) tan 66^(@)) =-1

Prove that :(tan69^(@)+tan66^(@))/(1-tan69^(@)tan66^(@))=-1

Prove that (tan69^@+tan66^@)/(1-tan69^@tan66^@)=-1 .

Prove that :(tan69^@+tan 66^@)/(1-tan 69^@tan66^@)=-1

Prove that : (i) "sin"105^(@)+cos105^(@)=(1)/(sqrt(2)) (ii) cos105^(@)+cos15^(@)="sin"75^(@)-"sin"15^(@)

tan 6 ^(@) tan 42 ^(@) tan 66 ^(@) tan 78^(@) =1

Prove that: tan6^(0)tan42^(0)tan66^(@)tan78^(@)=1

Prove that Cot105^(@)=-(2-sqrt(3))=-Tan15^(@)

Prove that : tan 69^@ + tan 66^@+ 1 = tan 69^@ tan 66^@ .