Hello S.,
Just to answer to an old unanswered question (and confirm that is now OK):
On activity diagram:
@startuml
start
:<math>int_-1^1 sqrt(1-x^2)dx = pi/2</math>;
:<math>...</math>;
end
@enduml
On component:
@startuml
node math [
<math>int_-1^1 sqrt(1-x^2)dx = pi/2</math>
]
@enduml
And in Visual Studio Code, this should work since it uses a plantuml server...
Regards,
Th.