Is line 3 of Great Vigor in its correct place?

It is in its correct place (當位): a yang line in an odd position or a yin line in an even one, which the tradition reads as a line at ease where it stands.

Hexagram 34, line 3

九三Line 3 of Great Vigor

Nine in the third place · 大壯 dà zhuàng

the ram and the fencebrute forcethe net of restraint

爻辭 The line text

小人用壯，君子用罔，貞厲。羝羊觸藩，羸其角。

The third line, undivided, shows, in the case of a small man, one using all his strength; and in the case of a superior man, one whose rule is not to do so. Even with firm correctness the position would be perilous. (The exercise of strength in it might be compared to the case of) a ram butting against a fence, and getting his horns entangled.

Its symbolism

小人用壯，君子罔也。

'The small man uses all his strength; in the case of the superior man it is his rule not to do so.'

In plain words

The small person uses force; the superior person uses the net. Line three is yang in a yang place at the top of Qian, the point where strength is at its fullest and least governed, and it corresponds to the top line, which the text describes as stuck. Its picture is the ram butting a fence and getting its horns caught. 罔 has two readings: Legge's 'rule of not doing so', following Cheng Yi who takes it as 無 — the superior person acts as if he had no strength — and the older 'net', a self-restraint that catches the impulse. Either way the warning is the same: even steadiness here is perilous (貞厲), because the position itself invites excess.

If this line is changing

When you can win by force, decline to; the fence you could break through today is the one your horns get caught in.

Where the line stands

A solid line, yang — written 九 (nine), the number of an old yang line that moves when cast.
It is in its correct place (當位): a yang line in an odd position or a yin line in an even one, which the tradition reads as a line at ease where it stands.
It belongs to the lower trigram 乾 Qian (the Creative) (heaven).
It corresponds (應) with line 6: one yin and one yang, the two lines answer each other across the hexagram.

之卦 When this line moves

大壯 Great Vigor becomes ䷵ 54 歸妹 Marrying the Younger Sister

Thunder over the lake: the younger sister married as a secondary wife. Undertakings bring misfortune; nothing is favourable — a relationship or position entered on unequal terms must be managed with great care.

What it becomes54 · 歸妹 Marrying the Younger Sisterguī mèi

The six lines of 大壯 Great Vigor

Read 大壯 Great Vigor for a question about

Love and relationships Work and career A yes-or-no decision

Questions about this line

What does Nine in the third place of hexagram 34, Great Vigor, mean?: The small person uses force; the superior person uses the net. Line three is yang in a yang place at the top of Qian, the point where strength is at its fullest and least governed, and it corresponds to the top line, which the text describes as stuck. Its picture is the ram butting a fence and getting its horns caught. 罔 has two readings: Legge's 'rule of not doing so', following Cheng Yi who takes it as 無 — the superior person acts as if he had no strength — and the older 'net', a self-restraint that catches the impulse. Either way the warning is the same: even steadiness here is perilous (貞厲), because the position itself invites excess.
What does hexagram 34 become when line 3 changes?: Great Vigor becomes hexagram 54, 歸妹 Marrying the Younger Sister: Thunder over the lake: the younger sister married as a secondary wife. Undertakings bring misfortune; nothing is favourable — a relationship or position entered on unequal terms must be managed with great care.
Is line 3 of Great Vigor in its correct place?: It is in its correct place (當位): a yang line in an odd position or a yin line in an even one, which the tradition reads as a line at ease where it stands.

Cast a reading Hexagram 34 in full Changing lines explained

Chinese text: the received Zhouyi (Wuyingdian lineage). English: James Legge, The Yî King, Sacred Books of the East XVI, 1882 (public domain).