Having sequence like $$ \beta_1 \cos\theta_1 + \beta_2 \cos\theta_2 + \beta_3 \cos\theta_3 + \dots + \beta_n \cos\theta_n$$ it is possible to present it using summation notation as follows:
$$ \sum_{i=1}^n \beta_i \cos\theta_i $$
But is it correct to present a sequence like
$$ \beta_1 \cos\theta_1 + \beta_2 \cos\theta_2 - \beta_3 \cos\theta_3 \pm \dots \pm \beta_n \cos\theta_n$$ as summation when a particular elements may need to be used with a negative sign?
Update 1
Unfortunately there is no any pattern for + and -. The sign is deduced by manually interpreting the contour of a polygon.
Update 2
Also, Is it correct for integration notation?