Pāṇini sūtras

The affix ṭach comes after go standing at the end of a Tatpurusha compound, when no elision of a Taddhita affix has taken place in forming such compound.

1. goḥगोः

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   gग्	goगो	goḥगोः	go [word]	goगो + plus ḥः

2. a+taddhita+lukiअ+तद्धित+लुकि

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   aअ	aअ	aअ	not	aअ
   tत्	taddhitaतद्धित	taddhitaतद्धित	taddhitaतद्धित	taddhitतद्धित् + plus aअ
   lल्	lukलुक्	lukiलुकि	suffix elision	lukलुक् + plus iइ

Anuvṛtti

1. samāsa+antāḥसमास+अन्ताः 5·4·68

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   sस्	samāsaसमास	samāsaसमास	Sanskrit compound	samāsसमास् + plus aअ
   aअ	antaअन्त	antāḥअन्ताः	end	antअन्त् + plus āMआM

2. tatpuruṣasyaतत्पुरुषस्य 5·4·86

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   tत्	tatpuruṣaतत्पुरुष	tatpuruṣasyaतत्पुरुषस्य	tatpuruṣaतत्पुरुष	tatpuruṣतत्पुरुष् + plus asyaअस्य

3. ṭacटच् 5·4·91

   Part	Lexeme	Sandhi form	Meaning	Stem
   ṭट्	ṭacटच्	ṭacटच्	ṭacटच्	ṭacटच्