$$cos^-1\frac{4}{5} + cos^-1\frac{12}{13}=cos^-1\frac{33}{65}$$ when the inverse function takes principal range.

Question

anonymous · Answer

@experimentX

anonymous · Answer

I think it is to show that the LHS is equal to the RHS.

experimentx · Answer

yes ... try taking  sin() of whole thing on both sides.

experimentx · Answer

anonymous · Answer

Then my teacher has given it wrong. :D But there are 3 more questions given. :(

anonymous · Answer

I checked another question and the wolfram alpha says it is true. Can you help me solve it?

experimentx · Answer

sure

anonymous · Answer

I changed the question. :)

anonymous · Answer

|dw:1395589144840:dw|