someone tell me why this answer is wrong...u are given final wavelength of 0.0022 nm, u want to solve for the intial wavelength using the compton scattering equation which is

final wl -intial wl= 0.002426(1-cos(theta)) theta is 45 degrees.

so initial w.l. = 0.002426(1-cos45)+0.0022 which is 0.00291 nm!!
just want to know why i got a point off