笑う and 喜ぶ: laughter, laughing at failure, and delight
Distinguish a baby's audible laughter from laughing at failure, then compare rejoicing at news of success. Preserve the proposal to encourage another attempt and the status of a gift being considered.
Read the target and context of 笑う
笑う (わらう) describes laughing. 「赤ん坊が初めて声を上げて笑う。」 says that a baby laughs out loud for the first time, without naming the cause of the laughter or explaining the baby's mood.
「失敗を笑うのではなく、次の挑戦を応援しよう。」 proposes encouraging the next attempt instead of laughing at failure. The target 「失敗」 gives the laughter its mocking sense here, while 「のではなく」 prevents the phrase from being read as a report that mockery already occurred.
The cause of delight and an anticipated response with 喜ぶ
喜ぶ (よろこぶ) describes being delighted or rejoicing. In 「合格の知らせを聞いて、家族は皆喜びました。」, the whole family rejoiced at the news of success; the sentence does not additionally report visible laughter.
In 「祖父が喜ぶ贈り物を兄弟で考えました。」, the siblings thought of a gift that would delight their grandfather. 「祖父が喜ぶ」 describes the kind of gift considered, rather than reporting a completed purchase, delivery, or delighted response from him.
Laughing and feeling pleased need not be identical
A baby's audible laughter, mockery directed at failure, and delight at news of success have different targets and contexts. 笑う does not always express a positive feeling, and 喜ぶ does not require an observable act of laughing.
The failure example proposes avoiding mockery and supporting another attempt. The gift example distinguishes considering a gift from its anticipated effect, so check whether an action or feeling mentioned inside a phrase is also reported as having occurred.
Does 「祖父が喜ぶ贈り物を兄弟で考えました。」 say that the grandfather received the gift and was delighted?
Show the answer and why
No. It says that the siblings thought of a gift that would delight him. It does not report buying or delivering the gift, or his actual response.