How do you solve #8cos^3x-1=0#?

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How do you solve #8cos^3x-1=0#?

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Answer 1 · 2016-08-07T03:02:02

#pi/3 + 2kpi#
#(5pi)/3 + 2kpi#

Explanation:

#cos^3 x = 1/8#
#cos x = 1/2#
Trig table and unit circle give 2 arcs x that have same cos value.
#cos x = 1/2# --> #x = +- pi/3#
The arc #(-pi/3)# is the same as the arc #(5pi)/3# --> (co-terminal)
General answers:
#x = pi/3 + 2kpi#
#x = (5pi)/3 + 2kpi#

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How do you solve #8cos^3x-1=0#?

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