A radio receiver is set up on a mast in the middle of a calm lake to track the radio signal from a satellite orbiting the Earth. As the satellite rises above the horizon, the intensity of the signal varies periodically. The intensity is at a maximum when the satellite is 1 = 3° above the horizon and then again at 2 = 6° above the horizon. What is the wavelength of the satellite signal? The receiver is h = 4.0 m above the lake surface.

Question

A radio receiver is set up on a mast in the middle of a calm lake to track the radio signal from a satellite orbiting the Earth. As the satellite rises above the horizon, the intensity of the signal varies periodically. The intensity is at a maximum when the satellite is 1 = 3° above the horizon and then again at 2 = 6° above the horizon. What is the wavelength  of the satellite signal? The receiver is h = 4.0 m above the lake surface.

I know that you are supposed to solve for the path length difference of the radio signal and that it acts like like as it is coming down to the receiver but i'm still having problems solving for lambda.