Video narration
Cylinder ka Curved Surface Area yani CSA yaad karte-karte ulajh jaate hain? Ise ratne ki zarurat nahi hai. Kisi cylindrical bottle ya dibbe par kagaz lapetiye. Kagaz chaaron or ghoomta hai, bilkul cylinder ki curved surface ki tarah. Ab us surface par upar se neeche tak ek seedha vertical cut lagaiye, aur use kagaz ki tarah khol dijiye. Dekhiye, curved hissa rectangle ban gaya. Us rectangle ki height, cylinder ki height h hi rehti hai. Uski length vah poori doori hai, jo kagaz ne bottle ke chaaron or tay ki. Yani cylinder ke base ki circumference. Circle ki circumference = 2pi r. Isliye rectangle ki length = 2pi r, aur height = h. Ab CSA ka formula alag se yaad mat kijiye. Rectangle ka area nikaaliye: length x height. Yani 2pi r x h = 2pi rh. Bas, cylinder kholo, rectangle pao. Uski length 2pi r aur height h, isliye curved surface area, CSA = 2pi rh.