SOLUTION: Find the exact value of sin (arccos[-2/5])

Algebra ->  Trigonometry-basics -> SOLUTION: Find the exact value of sin (arccos[-2/5])      Log On


   

Question 923467: Find the exact value of sin (arccos[-2/5])
Answer by lwsshak3(11628) About Me  (Show Source):
You can put this solution on YOUR website!
Find the exact value of sin (arccos[-2/5])
(arccos[-2/5]) reads:
the angle x whose cos=-2/5
cosx=-2/5
sin(arccos[-2/5])=sinx=√(1-cos^2x)=√(1-4/25)=√(21/25)=√21/5