# Math Help - How we know the answer of tan-1 of polar will be system Deg or rad

1. ## How we know the answer of tan-1 of polar will be system Deg or rad

Hi

How we know the answer of tan-1 of polar will be Deg or rad in calcolator

because i see in some questions the solving was Deg and anthor by rad

for example (write in polar)
1) -8 + 5i ----- > here we use rad to find tan-1
2) -3 - 5i ------> here we use deg to find tan-1

2. Originally Posted by r-soy
Hi

How we know the answer of tan-1 of polar will be Deg or rad in calcolator

because i see in some questions the solving was Deg and anthor by rad

for example (write in polar)
1) -8 + 5i ----- > here we use rad to find tan-1
2) -3 - 5i ------> here we use deg to find tan-1