When a siren is approaching you, how does the wavelength of the waves reaching you compare to the actual wavelength that the siren emits?

The wavelength of the sound waves are shorter.

Explanation: When a stationary observer hears an approaching sound in a moving source the observer hears a louder sound since the wavelength of each sound wave is shorter. And as the source moves away from the observer the sound becomes weaker since the wavelength of each sound wave increases causes weaker intensity.

the working equation for the angular size is the product of the physical size and 360 degrees divided by the product of two pi and distance from earth. the minimum size would be 0.559 degrees while the maximum size would be 0.49 degrees.