dy / dx = ( 3 - y ) cos x
Divide both sides by 3 - y
dy / [ dx ∙ ( 3 - y ) ] = cos x
Multiply both sides by dx
dy / ( 3 - y ) = cos x dx
Substitution:
3 - y = u
- dy = du
dy = - du
∫ dy / ( 3 - y ) = ∫ - du / u = - ∫ du / u = - log ( u ) + C₁ = - log ( 3 - y ) + C₁
∫ cos x dx = sin x + C₂
∫ dy / ( 3 - y ) = ∫ cos x dx
- log ( 3 - y ) + C₁ = sin x + C₂
Subtract C₁ to both sides
- log ( 3 - y ) = sin x + C₂ - C₁
C₂ - C₁ = C
- log ( 3 - y ) = sin x + C
Multiply both sides by - 1
log ( 3 - y ) = - sin x - C
e^[ log ( 3 - y ) ] = e^( - sin x - C )
3 - y = e^(- sin x ) ∙ e^( - C )
Subtract 3 to both sides
- y = e^( - sin x ) ∙ e^( - C ) - 3
Multiply both sides by - 1
y = - e^( - sin x ) ∙ e^( - C ) + 3
x = 0 , y = 1
y = - e^( - sin x ) ∙ e^( - C ) + 3
1 = - e^( - sin 0 ) ∙ e^( - C ) + 3
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- sin 0 = - ( 0 ) = 0
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1 = - e^0 ∙ e^( - C ) + 3
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e^0 = 1
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1 = - 1 ∙ e^( - C ) + 3
1 = - e^( - C ) + 3
Add e^( - C ) to both sides
1 + e^( - C ) = - e^( - C ) + e^( - C ) + 3
1 + e^( - C ) = 3
Subtract 1 to both sides
e^( - C ) = 2
y = - e^( - sin x ) ∙ e^( - C ) + 3
y = - e^( - sin x ) ∙ 2 + 3
y = - 2 e^( - sin x ) + 3
Consider the fifferential equation dy/dx=(3-y)cosx.Let y=f(x)be the particular solution to the differential equation with the inital condition f(0)=1.
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