She would need to play 50 minutes more to waste all her battery. In total 80 minutes.
The student that simplified the expression incorrectly is student 2
<h3>How to determine the incorrect result?</h3>
The steps are given as:

Student 1:
- Step 1:

- Step 2:

- Step 3: 1 + tan²(Ф)
- Step 4: sec²(Ф)
Student 2:
- Step 1:

- Step 2:

- Step 3: sec²(Ф)/tan²(Ф)
- Step 4: csc²(Ф)
As a general trigonometry rule;

This means that student 1 is correct, while student 2 is not
The first error in student 2's workings is in step 2, where we have:

The above expression is not justified and cannot be proved by any trigonometry rule
Since the step 2 is incorrect, the other steps cannot be used.
Hence, the student that simplified the expression incorrectly is student 2
Read more about trigonometric expressions at:
brainly.com/question/8120556
#SPJ1
Using symmetry concepts, it is found that there is a line of symmetry at x = 50, option D.
- A line symmetry is an imaginary line that runs through a graph, dividing it into two equal parts.
- A point symmetry is when every point is equidistant to the line of symmetry, but in opposite directions.
- In this problem, the values of x range from 0 to 100, being divided(definition changed) at 50, thus, there is a line of symmetry at x = 50, and option D is the correct one.
A similar problem is given at brainly.com/question/16679081
If you want to increase two opposite sides of a rectangle you're going to have to always decrease the remaining two sides by 20% to keep the area the same.