Asked by Miley
Determine the solution of the equetion: 2cos x-1=0? 2cos x=0? and 2cos x+1=0?
Answers
Answered by
Reiny
2cosx - 1 = 0
2cosx = 1
cosx = 1/2
I know from my basic trig relations that cos 60° = 1/2 and by the CAST rule cos 300° = 1/2
so x = 60° or x - 300° , or in radians: π/3, 5π/3
2cosx = 0
cosx = 0
I know from looking at a cosine curve that
x = 90° or x = 270° or in radians : π/2, 3π/2
do the third one the same way I did the first one
2cosx = 1
cosx = 1/2
I know from my basic trig relations that cos 60° = 1/2 and by the CAST rule cos 300° = 1/2
so x = 60° or x - 300° , or in radians: π/3, 5π/3
2cosx = 0
cosx = 0
I know from looking at a cosine curve that
x = 90° or x = 270° or in radians : π/2, 3π/2
do the third one the same way I did the first one
Answered by
Miley
The answer is 120 if i'm not mistaken
Answered by
Reiny
Since the cosine is negative in quads II or III, the answers would be 120° or 240°
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