Question

inverse trigonometry
pls help me​

Answer 1

Answer:

tan^-(1/4) + tan^-1(2/9)

= tan^-1[ (1/4 + 2/9)/(1-(1/4)(2/9) ) ]

=tan^-1 [ ((9+8)/36) / (1-1/18) ]

=tan^-4 [ (17/36)/(17/18) ]

=tan^-1 [(1/2)]

by pythagoras c² = (1)² + 2² = 5

=> c = √5

=> cos^-1(2/√5)

hence... proved