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Question Number 65192 by naka3546 last updated on 26/Jul/19

Minimum  value  of            ∣ sin x + cos x + tan x + cot x + sec x + cosec x ∣   is  ...

Minimumvalueofsinx+cosx+tanx+cotx+secx+cosecxis...

Answered by Tanmay chaudhury last updated on 26/Jul/19

sinx+cosx →(let sinx+cosx=a)  (√2) ((1/(√2))sinx+(1/(√2))cosx)  (√2) sin(x+(π/4))   (√2) ≥(√2) sin(x+(π/4))≥−(√2)   (√2)≥a≥−(√2)  so   (√2) ≥sinx+cosx≥−(√2)   tanx+cotx  =(1/(sinxcosx))=(2/(sin2x))=(2/(−1+1+sin2x))  =(2/(−1+(sinx+cosx)^2 ))=(2/(a^2 −1))  secx+cosecx  =(1/(cosx))+(1/(sinx))  =((2(sinx+cosx))/(sin2x))  =((2(a))/(a^2 −1))  now ∣sinx+cosx+tanx+cotx+secx+cosecx∣  =∣a+(2/(a^2 −1))+((2a)/(a^2 −1))∣  =∣a+2×((a+1)/((a+1)(a−1)))∣  =∣a+(2/(a−1))∣  put a=(√2)   =∣(√2) +((2((√2) +1))/(((√2) −1)((√2) +1)))∣  =∣(√2) +2(√2) +2∣  =3(√2) +2  =6.23  put a=−(√2)   ∣−(√2) +(2/(−(√2) −1))∣  ∣−(√2) −((2((√2) −1))/1)∣  ∣−(√2) −2(√2) +2∣  ∣2−3(√2) ∣  ∣−2.23∣  =2.23  put a=0  ∣a+(2/(a−1))∣  =∣0+(2/(−1))∣  =2  so minimum value is 2  pls check

sinx+cosx(letsinx+cosx=a)2(12sinx+12cosx)2sin(x+π4)22sin(x+π4)22a2so2sinx+cosx2tanx+cotx=1sinxcosx=2sin2x=21+1+sin2x=21+(sinx+cosx)2=2a21secx+cosecx=1cosx+1sinx=2(sinx+cosx)sin2x=2(a)a21nowsinx+cosx+tanx+cotx+secx+cosecx=∣a+2a21+2aa21=∣a+2×a+1(a+1)(a1)=∣a+2a1puta=2=∣2+2(2+1)(21)(2+1)=∣2+22+2=32+2=6.23puta=22+22122(21)1222+22322.23=2.23puta=0a+2a1=∣0+21=2sominimumvalueis2plscheck

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