Final answer:
An equivalent expression for cd can refer to the unit of luminous intensity, candela (cd), or a multiplication operation between two variables representing an expression.
Step-by-step explanation:
An equivalent expression for cd in this context can refer to the unit of luminous intensity, candela (cd), or a multiplication operation between two variables representing an expression.
In the context of luminous intensity, cd refers to the unit of measurement. It is defined as the luminous efficacy of monochromatic radiation of frequency 540×10¹² Hz, with a value of 683 cd.sr.W¹, or cd sr kg ¹m-².s³. This definition is based on the SI unit system.
On the other hand, in the context of mathematical expressions, cd can represent the product of two variables. For example, if c represents the circumference of a circle and d represents the diameter, then cd represents the formula for calculating the circumference, which is equal to π times the diameter.