为什么 “也” 发音为 "ye" 但是 “他”发音为"ta"？？？ Oh great. I have to ask in English to get it past StackExchange filters.
Characters with radicals typically have pronunciations close to the bare character.
For example: "韦“ (wei) versus "伟“ (wei) or "敢“ (gan) versus "憨“ (han)
But "也" (ye) and "他“ (ta) are very much exceptions. Why?

有部首旁的汉字的发音通常按照没有部首旁的字。 例如 “韦”/”伟“、 “清”/“青”、 “敢”/“憨”等。

但是 “也”/“他” 根本在例外。为什么？
Please refer to Old Chinese reconstructions when analysing phonetic components of characters.

他 - Baxter-Sagart OC: /*l̥ˤaj/ > MC: /tʰɑ/ > Mandarin Pinyin: tā

也 - Baxter-Sagart OC: /*lAjʔ/ > MC: /jiaX/ > Mandarin Pinyin: yě


  有部首旁的汉字的发音通常按照没有部首旁的字。


You should probably learn that 部首 is a dictionary indexing tool, and has nothing to do with the functions of character components.