Answer:
Each processes' products is the other one's reactants
Step-by-step explanation:
Photosynthesis takes carbon dioxide and sunlight to create oxygen and glucose, or sugars.
Cellular Respiration takes glucose and oxygen and turns them into carbon dioxide and water molecules.
As humans and animals breathe out, we are giving the plants the carbon dioxide they need to perform photosynthesis. When photosynthesis is finished, humans and animals use the byproduct of oxygen and use cellular respiration to create more carbon dioxide.
Without one, we couldn't have the other. : )