use a double angle identity to find the exact value of the expression cos 420 please help!!!
A adpcane15 New member Joined Apr 12, 2007 Messages 12 Apr 17, 2007 #1 use a double angle identity to find the exact value of the expression cos 420 please help!!!
stapel Super Moderator Staff member Joined Feb 4, 2004 Messages 16,582 Apr 17, 2007 #2 Please reply showing all of your work and reasoning so far. You've reduced "420" to an equivalent angle between 0 and 360, and... then what? Thank you. Eliz.
Please reply showing all of your work and reasoning so far. You've reduced "420" to an equivalent angle between 0 and 360, and... then what? Thank you. Eliz.
