advanced functions
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Determine approximate solutions for this equation in the interval x is all real numbers [0, 2pi), to the nearest hundredth of a radian:
cosx + 0.75 = 0

cosx = .75
the cosine is negative in II and III
take inverse cosine of +.75, this will give you the reference angle
for angle in II, take pi  reference angle
for angle in III take pi + reference angle