How can i solve this without a calculator? Cos ^-1 (1/2) Cos ^-1 (-1/2)
L ladyazpy New member Joined Mar 1, 2005 Messages 31 Apr 26, 2006 #1 How can i solve this without a calculator? Cos ^-1 (1/2) Cos ^-1 (-1/2)
tkhunny Moderator Staff member Joined Apr 12, 2005 Messages 11,339 Apr 26, 2006 #2 If a=cos−1(1/2)\displaystyle a = cos^{-1}(1/2)a=cos−1(1/2), then cos(a) = 1/2. That value should be on any chart of values that you should memorize.
If a=cos−1(1/2)\displaystyle a = cos^{-1}(1/2)a=cos−1(1/2), then cos(a) = 1/2. That value should be on any chart of values that you should memorize.
pka Elite Member Joined Jan 29, 2005 Messages 11,988 Apr 26, 2006 #3 Do you know a standard acute angle, Θ, such cos(Θ)=1/2 ? Then the equivalent angle in the second quadrant cos(π−θ)=−1/2\displaystyle \cos (\pi - \theta ) = - 1/2cos(π−θ)=−1/2.
Do you know a standard acute angle, Θ, such cos(Θ)=1/2 ? Then the equivalent angle in the second quadrant cos(π−θ)=−1/2\displaystyle \cos (\pi - \theta ) = - 1/2cos(π−θ)=−1/2.
