Degrees, Grads, and Radians

There are three methods of measuring angles: degrees, grads, and radians. However, the ZX81 with all its new trigonometric functions can only measure angles in radians. You can convert a measurement by any of the three methods to either of the remaining methods with the few short programs given in the listings below. You may want to add a REM statement to identify each listing for use in a program.