Question

What is the largest value of "x" (in radians) less than pi satisfying the equation: cos x = cos (6x)

Answer 1

0

Answer 2

is it the largest though?

Answer 3

http://www.wolframalpha.com/input/?i=graph+cos%28x%29%2C+cos%286x%29+from+0+to+pi

Answer 4

it's the largest value of x, not the largest value of solution

Answer 5

right, I misunderstood

Answer 6

i'm getting x=4pi/5

Answer 7

\[\cos(x+2 \pi n)=\cos(6x) => x+2\pi n=6x\]

Answer 8

http://www.wolframalpha.com/input/?i=graph+cos%28x%29%2C+cos%286x%29+from+2.69+to+2.695

Answer 9

\[5x=2\pi n => x=\frac{2 \pi n}{5}\]

Answer 10

so if n=4
x<pi

Answer 11

oops n=2

Answer 12

Myininaya is right

Answer 13

ok thank you

Answer 14

What's the Python solution to this problem?

import sympy.

sympy.solve(cos(x) = cos(6x))