From the seventeenth century, scales of trigonometric functions appeared on drawing instruments such as rules and sectors. The discovery of the logarithm at the beginning of the century led to another instrument for carrying out routine calculations, the slide rule. Some slide rules also had scales of logarithmic trigonometric functions. Slide rules would become a common tool of calculation for scientists and engineers around 1900, and sold until the introduction of inexpensive electronic calculators in the 1970s.