If three angles A, B and C are in arithmetic progression, Prove that \(cotB=\frac { sinA-sinC }{ cosC-cosA } \)

Find sin105^o + cos105^o

Find the principal value of tan^-1(-\(\sqrt{3}\))

Evaluate the following tan\(\left(\cos ^{-1} \frac{8}{17}\right)\)

Prove that \({ \cos }^{ -1 }\left( \frac { 4 }{ 5 } \right) +{ \cos }^{ -1 }\left( \frac { 3 }{ 5 } \right) ={ \cos }^{ -1 }\left( \frac { 27 }{ 11 } \right) \)