"슬프다(descriptive verb, adjective in Korean)" conjugated like....
1. The past tense
슬펐습니다 <= 슬ㅍ + 었(the past suffix) + 습니다
2. The present tense
슬픕니다 <= 슬ㅍ + ㅂ니다
3. The future tense
슬플 것입니다 <= 슬ㅍ + ㄹ 것입니다
The formal sentences end with "-ㅂ니다" or "습니다".
\^o^/