How can i solve this without using my calculator

ladyazpy

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Joined
Mar 1, 2005
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31
How can i solve this without a calculator?

Cos ^-1 (1/2)

Cos ^-1 (-1/2)
 

tkhunny

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Apr 12, 2005
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If \(\displaystyle a = cos^{-1}(1/2)\), then cos(a) = 1/2. That value should be on any chart of values that you should memorize.
 

pka

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Jan 29, 2005
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8,670
Do you know a standard acute angle, Θ, such cos(Θ)=1/2 ?
Then the equivalent angle in the second quadrant \(\displaystyle \cos (\pi - \theta ) = - 1/2\).
 
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