How do you evaluate #cos(csc^-1((2sqrt2)/5))# without a calculator?
1 Answer
Sep 7, 2016
Invalid expression.
Explanation:
Let #a = csc^(-1)((2sqrt 2)5) in Q1, for the principal value, wherein
cosine is positive. Then,
csc a =(2 sqrt 2)/5. The reciprocal sin a = 5/(2sqrt 2) = 1.76... > 1.
And so, a is unreal. The given expression is invalid..
