find the exact value of the given expression. Thank you!

tan(1/2cos^-1(9/10)

2 answers

tangent of 1/2 the angle whose cosine is 9/10

Exact value? What is wrong with a calculator? Paste this into your google search window...

tan(.5*arccos(9/10))=

Is that exact enough? It appears to be an irrational number.
find the exact value of (5pie/8)