What gas law assumes constant temperature?

The gas law that assumes constant temperature is Boyle's Law. It states that the pressure of a given quantity of gas is inversely proportional to its volume when the temperature is held constant. In formula terms, this is expressed as ( P_1 V_1 = P_2 V_2 ), where ( P ) represents pressure and ( V ) represents volume. Thus, if the volume decreases, the pressure increases, provided the temperature remains unchanged.