Question about latex synthax

I am writing a formula in latex to insert into matlab. The problem is that I need to write an integral with has as interval y1(x) to y2(x)

I wrote $$I(f)=\int_a^b \int_ y1(x)^y2(x) f(x,y) \dy \dx$$ the problem is that the second intégral comes out wrong: instead of getting a subscript y1(x)and a superscript y2(x), I only get a subscript y, the rest comes out flatlined.

Any help?

Answer 1

[Honglei Chen]

add {} around y1(x) and y2(x), like this

$$I(f)=\int_a^b \int_ {y1(x)}^{y2(x)} f(x,y) \dy \dx$$

[Karel]

thank you, that did it