1.

(i) The degree of the differential Equation \(\frac{d^2y}{dx^2}\)+cos\((\frac{dy}{dx})\)=0 is(a) 2(b) 1(c) 0(d) Not defined(ii) Solve \(\frac{dy}{dx}\) + 2y tanx = sinx; y = 0, x = \(\frac{\pi}{3}\)

Answer»

(i) (d) Not defined.

(ii) \(\frac{dy}{dx}\) + 2y tanx = sinx

Then, P = 2tanx, Q = sinx

IF = e∫Pdx = e∫2tanxdx = e2log sec x = sec2 x 

Solution is; y × IF = ∫Q(IF)dx + c

⇒ ysec2 x = ∫sinx sec2 xdx + c

⇒ ysec2 x = ∫tanx secx dx + c

⇒ ysec2x = secx + c

Here; y = 0, x = \(\frac{\pi}{3}\)

⇒ 0 × sec2 \(\frac{\pi}{3}\)= sec \(\frac{\pi}{3}\) + c ⇒ c = -2

⇒ ysec2 x = secx – 2.



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