How would you find the perihelion distance of Mars?

Both perihelion and aphelion distances can be computed from semi.-major axis a and eccentricity e of Mars elliptic orbit. They are a(1 - e) and a(1 + e)

a = 1.52 AU and e = 0.09. So, Rounded to three significant digits (sd) perihelion = 1.38 AU and aphelion = 1.66 AU, nearly. Distance unit AU = 'a' for Earth. For more sd in the values, 'a' and 'e' for Mars should be in that many or more sd..