Sum of roots of trigonometric equation This is the hardest problem on Georgian (country) high school math exam. Find all values for parameter a for which the sum of all the roots of the equation: sin(sqrt (ax-x^2))=0 equal to 100. Note that you can't use calculus and we assume only real roots!

Tessa Peters

Tessa Peters

Answered question

2022-10-22

Sum of roots of trigonometric equation
This is the hardest problem on Georgian (country) high school math exam.
Find all values for parameter a for which the sum of all the roots of the equation:
sin ( a x x 2 ) = 0
equal to 100
Note that you can't use calculus and we assume only real roots!

Answer & Explanation

Dana Simmons

Dana Simmons

Beginner2022-10-23Added 14 answers

Hint: what is the sum of the roots of a x x 2 = n π?
Chelsea Pruitt

Chelsea Pruitt

Beginner2022-10-24Added 5 answers

We have a > 0, and the equation reads
a x x 2 = k 2 π 2 .
By Vieta, when you add the roots in pairs, the sum is a
Hence with k 0
( k + 1 ) a = 100
with
a 2 k π
or
( k + 1 ) a = 100 4 ( k + 1 ) k π .
Finally,
a = 100 k + 1
with k = 0 , 1 , 2.
Note that as a is rational and π transcendental, there is no risk of equal roots.

Do you have a similar question?

Recalculate according to your conditions!

Ask your question.
Get an expert answer.

Let our experts help you. Answer in as fast as 15 minutes.

Didn't find what you were looking for?