berrypicking
solve equation in the interval from 0 to 2pi.
7 cos 2t =3
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berrypicking
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corrections 7 cos 2t=3
cwrw238
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arccos 3/7 - your calculator will give u the value of t in first quadrant
the other value is in 4th quadrant
berrypicking
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what does arccos mean
berrypicking
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am I setting calculator in rad. or degrees
cwrw238
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oh - then find angle whose cos is 3/7 0 calculator will give you value of 2t in first quadrant
cwrw238
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right - set to rad arccos means the angle whose cos is given value
or - on calculator button this might be cos -1
berrypicking
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cos 3/7= .91 now what
berrypicking
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how do I get the other value
cwrw238
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you need cos-1 not cos
check again : i make it 1.128 rad
berrypicking
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ok that is 1.099??
berrypicking
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1/cos(3/7) right?
berrypicking
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and how do you know I need cos-1 and not cos?
cwrw238
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no - the cosine of the angle 2t = 3/7
you need to find the angle whose cosine is 3/7
first find 3 / 7 on ur calculator
then you need to press the cos-1 (or arccos) button
berrypicking
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do I just press cos then -1
cwrw238
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cos-1 does not mean 1 / cos in this context
cwrw238
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no there is probably a button marked cos but you first press the shift key then cos button to get value of the angle
cwrw238
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cos-1 notation is a bit confusing - in Europe they use arccos which makes more sense
berrypicking
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cos (3/7)=.91. Do I press shift key before entering cos (3/7)? don't know the shift key
berrypicking
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I haven't done any problems with cos-1
cwrw238
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calculators vary
you either press shift cos (3/7)
or (3/7) shift cos
cwrw238
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the correct value is 1.127 (to 3 dec places)
cwrw238
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sorry 1.128
cwrw238
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its a bit hard to explain without seeing your calculator....