expression that changes if a condition is true

Hi! I know it's a silly question but I don't remember how to write an expression like that

theta=psi+pi*(condition:x<0)

and I want -theta=psi if the condition is false

-theta=psi+pi if the condition is true

thanks!

Answer 1

[Ameer Hamza]

This is the correct syntax

theta = psi+pi*(x<0)

[Valeria Leto]

thanks

[Ameer Hamza]

I am glad to be of help!