Play the chord as given in the sheet music. According to Piano World, all major and minor chords have major and minor third intervals between their root and third tones. A major third is four half-steps; a minor third is three half-steps.
Find the number of half-steps that exist between notes by counting the number of white and black keys it takes to reach the note.
Look for the three notes that have two third intervals separating them. There should be seven half-steps to move from the root note to the fifth.
Look for two notes separated by five half-steps--also known as a perfect fifth--for another method of finding the root of a major or minor chord. Major and minor chords include the root, third and fifth by default, but sometimes include the octave. The octave of the root is a fifth above the fifth of the chord.