Yes, 正弦余弦正接プロ is completely free and it doesn't have any in-app purchases or subscriptions.
Not enough reviews to make a reliable assessment. The app needs more user feedback.
正弦余弦正接プロ is free.
To get estimated revenue of 正弦余弦正接プロ app and other AppStore insights you can sign up to AppTail Mobile Analytics Platform.