Question

Verify that the function y = a cos x + b sin x, where, a, b ∈ R is a solution of the differential equation d2y/dx2 + y=0...
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Answer 1

Step-by-step explanation:

ᵗʰᵉ ᵍⁱᵛᵉⁿ ᶠᵘⁿᶜᵗⁱᵒⁿ ⁱˢ ʸ = ᵃ ᶜᵒˢ ˣ + ᵇ ˢⁱⁿ ˣ … (1)

ᵈⁱᶠᶠᵉʳᵉⁿᵗⁱᵃᵗⁱⁿᵍ ᵇᵒᵗʰ ˢⁱᵈᵉˢ ᵒᶠ ᵉᵠᵘᵃᵗⁱᵒⁿ (1) ʷⁱᵗʰ ʳᵉˢᵖᵉᶜᵗ ᵗᵒ ˣ,

ᵈʸ/ᵈˣ = – ᵃ ˢⁱⁿˣ + ᵇ ᶜᵒˢ ˣ

ᵈ2ʸ/ᵈˣ2 = – ᵃ ᶜᵒˢ ˣ – ᵇ ˢⁱⁿˣ

ˡʰˢ = ᵈ2ʸ/ᵈˣ2 + ʸ

= – ᵃ ᶜᵒˢ ˣ – ᵇ ˢⁱⁿˣ + ᵃ ᶜᵒˢ ˣ + ᵇ ˢⁱⁿ ˣ

= 0

= ʳʰˢ

ʰᵉⁿᶜᵉ, ᵗʰᵉ ᵍⁱᵛᵉⁿ ᶠᵘⁿᶜᵗⁱᵒⁿ ⁱˢ ᵃ ˢᵒˡᵘᵗⁱᵒⁿ ᵒᶠ ᵗʰᵉ ᵍⁱᵛᵉⁿ ᵈⁱᶠᶠᵉʳᵉⁿᵗⁱᵃˡ ᵉᵠᵘᵃᵗⁱᵒⁿ.

ʰᵒᵖᵉ ⁱᵗ'ˢ ʰᵉˡᵖ ᵘʰ ❤️

Answer 2

Answer:

Y= a cosx + b sinx

dy/dx = - a sinx +b cosx

d2y/dx2= - a cos x - b sinx

LHS

d2y/dx= - a cosx - b sinx

LHS =d2y/dx2 +y

=. - a cosx - b sinx +a cosx + b sinx

=0

= RHS

HENCE, Verified