LOR From Math Department for Engg Grad School?

[AlkaKadri]

So I'm doing a double degree between Chemical Engineering and Pure & Applied Mathematics, and while I have 3 LOR writers from my Chem Engg department in mind, there's a prof in the Math department at my school that I feel could write a strong LOR for me. I'm planning to apply to apply to chem engg graduate programs, but I'm wondering what they'd think of getting an LOR from someone not in the field? I've not done research for this professor, but I'm confident that he can attest to my critical thinking abilities through the many proofs I've had to write in his upper year classes. We also get along quite well on a personal level, so I'm confident that this one would be one of the more enthusiastic letters.

Thoughts?

Edited August 3, 2018 by AlkaKadri