For complex mathematical problems that require a scientific calculator, you can count on Scientific Calculator Plus 991. This application will help you with advanced arithmetic problems for engineering and mathematics major students at the high school and university levels. 

The application has the following key inclusions:

• Basic 300 plus
• Advanced 115 plus
• Scientific 991
• Graphing  84 plus
• Integral 991 plus

This app offers comprehensive functions, from basic to advanced mathematical operations. It's a useful tool for calculating percentage, powers, roots, trigonometric, logarithms, derivatives, and more. It can also compute infinity numbers, prime factors, random numbers, combinations, permutations, GCD and LCM, and more.