# Find the number of pairs (m, n) of positive integers with 1 `<=` m < n `<=` 30, such that there exists a real number x satisfying sin(mx) + sin(nx) = 2.

The total number of pairs that satisfy the given conditions is 28.

## Expert Answers The number of pairs (m,n) of positive integers satisfying `1lt=mltnlt=30` have to be determined so that a real number x exists that allows `sin(mx) + sin(nx) = 2` .

For the sine function, the maximum value of sin x is 1 when `x = (2*N*pi+pi/2)` for an integer N.

If `sin(mx) + sin(nx) = 2` , then both `sin (mx)` and `sin (nx)` should be equal to 1.

As m and n are positive integers, `x = pi/2` .

For `1lt=mltnlt=30` , the possible pairs of m and n are

(1, 5), (1, 9), (1,13), (1,17), (1,21), (1,25), (1,29)

(5, 9), (5,13), (5,17), (5,21), (5,25), (5,29)

(9,13), (9,17), (9,21), (9,25), (9,29)

(13,17), (13,21), (13,25), (13,29)

(17,21), (17,25), (17,29)

(21,25), (21,29)

(25,29).

The total number of pairs that satisfy the given conditions is 28.

Last Updated by eNotes Editorial on ## We’ll help your grades soar

Start your 48-hour free trial and unlock all the summaries, Q&A, and analyses you need to get better grades now.

• 30,000+ book summaries
• 20% study tools discount
• Ad-free content
• PDF downloads
• 300,000+ answers
• 5-star customer support