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Question Number 76232 by Rio Michael last updated on 25/Dec/19

how do we find   ∫_0 ^(π/2)  sinh^(−1) x dx and  ∫_0 ^(π/2) cosh^(−1) xdx

howdowefindπ20sinh1xdxandπ20cosh1xdx

Commented by mr W last updated on 25/Dec/19

cosh^(−1)  x is defined for x≥1!

cosh1xisdefinedforx1!

Commented by turbo msup by abdo last updated on 25/Dec/19

let I =∫_0 ^(π/2)  argsh(x)dx  ⇒I =_(argsh(x)=t)    ∫_0 ^(argsh((π/2))) t ch(t)dt  =∫_0 ^(ln((π/2)+(√(1+(π^2 /4)))))  tcht()dt  =_(by parts)   [tsh(t)]_0 ^(ln((π/2)+(√(1+(π^2 /4)))))   −∫_0 ^(ln((π/2)+(√(1+(π^2 /4))))) sh(t)dt  =ln((π/2)+(√(1+(π^2 /4))))(((π/2)+(√(1+(π^2 /4)))−((π/2)+(√(1+(π^2 /4))))^(−1) )/2)  −(1/2)((π/2)+(√(1+(π^2 /4))))+((π/2)+(√(1+(π^2 /4))))^(−1) )

letI=0π2argsh(x)dxI=argsh(x)=t0argsh(π2)tch(t)dt=0ln(π2+1+π24)tcht()dt=byparts[tsh(t)]0ln(π2+1+π24)0ln(π2+1+π24)sh(t)dt=ln(π2+1+π24)π2+1+π24(π2+1+π24)1212(π2+1+π24)+(π2+1+π24)1)

Answered by mind is power last updated on 25/Dec/19

u=sh^− (x)  by part  ∫sh^− (x)dx=[xsh^− (x)]−∫(x/(√(1+x^2 )))dx  =xsh^− (x)−(√(x^2 +1))+c  sam with ch^− (x)

u=sh(x)bypartsh(x)dx=[xsh(x)]x1+x2dx=xsh(x)x2+1+csamwithch(x)

Answered by mr W last updated on 25/Dec/19

∫_0 ^(π/2) sinh^(−1)  x dx  =(π/2)sinh^(−1)  ((π/2))−∫_0 ^(sinh^(−1)  ((π/2))) sinh y dy  =(π/2)sinh^(−1)  ((π/2))−[cosh (sinh^(−1)  (π/2))−1]  =(π/2)ln ((π/2)+(√(1+((π/2))^2 )))+1−(√(1+((π/2))^2 ))  ≈1.075329

0π2sinh1xdx=π2sinh1(π2)0sinh1(π2)sinhydy=π2sinh1(π2)[cosh(sinh1π2)1]=π2ln(π2+1+(π2)2)+11+(π2)21.075329

Commented by mr W last updated on 25/Dec/19

Commented by mr W last updated on 25/Dec/19

I_1 =∫_0 ^(π/2) sinh^(−1)  x dx  I_2 =∫_0 ^(sinh^(−1)  (π/2)) sinh y dy  I_1 +I_2 =(π/2)×sinh^(−1)  (π/2)  I_2  is easier to get than I_1 .

I1=0π2sinh1xdxI2=0sinh1π2sinhydyI1+I2=π2×sinh1π2I2iseasiertogetthanI1.

Commented by Rio Michael last updated on 25/Dec/19

thanks

thanks

Commented by mr W last updated on 25/Dec/19

i also used this method in Q#76146.

You can't use 'macro parameter character #' in math mode

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