+P(x)y=Q(x), where, P(x)=−tan‌x and Q(x)=−secx IF‌=e∫P(x)‌dx=e∫−tan‌x‌dx ‌=eln|cos‌x|=|cos‌x| So, the general solution is y⋅‌ IF ‌‌=∫A(x)⋅‌ IF ‌dx+C y⋅cos‌x‌=∫−secx⋅cos‌x‌dx+C ‌=−∫dx+C=−x+C ‌=y=‌
−x+C
cos‌x
Given, f(0)=1 ⇒‌‌y=1‌ and ‌x=0 So, 1=‌