parametric equations

for some value of the parameter t. These are parametric equations for the line. They are most easily established by using the vector equation of the line and taking components. If none of l, m, n is zero, the equations can be written

which can be considered to be another form of the parametric equations, or called the equations of the line in ‘symmetric form'. If, say, n =  0 and l and m are both non-zero, the equations are written

if, say, m =  n =  0, they become y =  y1, z =  z1.

More generally in n-dimensional space, if p and a are in Rn with a ≠ 0, then

is a parameterization of the line passing through p which is parallel to a.

• impulse
• incentre
• incidence
• incircle
• inclination
• inclined plane
• include
• inclusion
• inclusion–exclusion principle
• inclusive disjunction
• incommensurable
• incompatible
• incompressible
• inconsistent
• increasing function
• increasing sequence
• increment
• indefinite integral
• independent
• independent events
• independent random variables
• independent variable
• independent variable
• indeterminate
• indeterminate equations