The rules that use the category "<digit-1>" are:

<degree_number-180-sing>

<digit-0> <digit-0> <digit-1>

<degree_number-360-sing>

<digit-0> <digit-0> <digit-1>

<degree_number-180-pl>

<digit-0-pl> <digit-1> <digit>

<digit-1> <digit-8> <digit-0>

<digit-1> <digit_zero_to_seven> <digit>

<degree_number-360-pl>

<digit-0-pl> <digit-1> <digit>

<degree_setting_in_tens-180>

<digit-1> <digit-not_8_or_9> <answer>

<digit-1> <digit-not_9>

<ordered_distance>

range <digit-1> <digit-zero> <digit-zero>

<degree_number-360-digit_sequence-pl>

<digit-0-pl> <digit-1> <digit>