Why is -LSB- math -RSB- \ tan -LRB- - \ theta -RRB- = - \ tan \ theta -LSB- / math -RSB- and -LSB- math -RSB- \ cot -LRB- - \ theta -RRB- = - \ cot \ theta -LSB- / math -RSB- ?
Why is -LSB- math -RSB- \ tan -LCB- \ theta -RCB- = \ frac -LCB- \ sin -LCB- \ theta -RCB- -RCB- -LCB- \ cos -LCB- \ theta -RCB- -RCB- -LSB- / math -RSB- ?