How do you solve sec(x)-1=tan(x)?

2 Answers
Mar 6, 2018

x=2kpi,kinZ

Explanation:

secx-1=tanxrArr1/cosx-1=sinx/cosxrArr1-cosx=sinxrArrcosx+sinx=1rArr1/sqrt(2)cosx+1/sqrt(2)sinx=1/sqrt(2)
rArrcosxcos(pi/4)+sinxsin(pi/4)=cos(pi/4)
rArrcos(x-pi/4)=cos(pi/4)
x-pi/4=2kpi+-pi/4,kinZ
x=2kpi+-pi/4+pi/4,kinZ
x=2kpi+pi/4+pi/4,kinZorx=2kpi-pi/4+pi/4.kinZ
color(red)(x=2kpi+pi/2,kinZorx=2kpi,kinZ)
But, taking k=0,..etc.
x=2kpi+pi/2.kinZ=>x=pi/2, which does not satisfy
secx-1=tanx, as sec (pi/2) and tan(pi/2) are undefined.
So, color(red)(x!=2kpi+pi/2,kinZrArrx=2kpi,kinZ)

Mar 6, 2018

x = 2kpi , "where k any integer"

Explanation:

sec(x)−1=tan(x)

1/cosx −1=sinx/cosx

(1-sinx)/cosx =1

sinx + cosx = 1, "where" cosx ≠ 0

x = 2kpi , "where k any integer"