「、？」「、」
'Huh, tangent is sine divided by cosine, right?' 'No, the other way around.'
Literal
'Huh, tangent [topic-って] sine [with-で] cosine [object-を] divide [explanatory reminder-んだっけ]?' 'Reverse, reverse.'
Quick math-homework dialogue. The math terms タンジェント, サイン, and コサイン are all katakana loanwords from English, not using the native Sino-Japanese equivalents. The division structure [X]で[Y]を割る means 'divide Y by X' — で marks the divisor, not the divisee. んだっけ is the reminder-seeking question marker. 逆、逆 is an emphatic doubled exclamation 'the opposite, (it's) the opposite.' Speaker 1 has the formula backwards (tan = sin/cos, not cos/sin).