Let's imagine the graphic of the sine function, and we take an interval from . if we take a string, or a metric tape, and measure the graphic, what would be its length?. what about other functions? if we take a linar function, it is easy, you just use the formula L(sq)=(a-b)sq + (f(a) - f(b))sq. but it does not work like that with other graphics. ane possible solution would be to divide the graphic in small intervals, and take the distance from each of their borders or from the center of one to the next, and add up all this results, nd make the intervals every time smaller, but how do you express that in mathematic language?.

thanks