Solution:
Give the following below

To find the cosine function, we will apply the general formula for cosine function below

To find the value of b


Substitute the values of the variables into the general formula for cosine function

Applying a graphing tool,
The graph of one cycle of the function is shown below
we are given
Mark clean his father's office in 30 minutes
so, the amount of work done by Mark in 1 minute is 
younger sister Lynn can clean the office in 40 minutes
so, the amount of work done by younger sister Lynn in 1 minute is 
total work done by them in 1 minute is 
now, we can simplify it



total time taken to complete same work is
........Answer
Answer:
1/4
Step-by-step explanation:
1 hour 15 minutes = 75 minutes
25 mins + 75mins = 100 minutes
25/100 minutes x 100 = 25%
25% = 1/4 of the time was spent reading.
Answer: 1/8 of a mile
Step-by-step explanation: because 3/8 minus 1/4 is 1/8