Last updated on .From the section Scottish Cup

Celtic took a huge step towards securing back-to-back trebles as they ruthlessly swept Rangers aside to reach the Scottish Cup final.

Celtic were commanding against passive opponents, with Tom Rogic and Callum McGregor scoring before half-time.

Rangers' woes worsened after the break, with Ross McCrorie dismissed for pulling back Moussa Dembele, who converted the resulting penalty.

Olivier Ntcham added the fourth, also from the spot, before the end.

With Dembele hitting the post early on, Ntcham firing wide and McGregor driving over, the scoreline might have been more emphatic for Celtic.

Rangers endured a chastening afternoon in a one-sided Old Firm semi-final

Rangers gathered only frustration and angst, with Andy Halliday hollering his frustration from the bench after being replaced by Josh Windass before half-time, and Daniel Candeias heading straight up the tunnel after he was substituted.

Celtic are now one league win away from retaining their seventh consecutive Premiership title, and face Motherwell in next month's Scottish Cup final, having already secured the League Cup last November.

Football matches are won and lost in a variety of ways. It is arguable that Rangers lost this one before kick-off.

Tactically, Rangers manager Graeme Murty appeared to get it wrong, and played into Celtic's hands. How they exploited it.

A midfield three sat deep to cater for James Forrest, McGregor and Rogic, a trio of sprightly attacking midfielders. It backfired spectacularly.

Rangers midfielder Andy Halliday was substituted before half-time

Celtic, in contrast, looked sharp from the off and almost took the lead when Dembele volleyed Ntcham's cross off the upright.

Rangers escaped, but it was the briefest of respites. Brendan Rodgers' side swarmed forward, exploiting Rangers' timid approach.

The opener soon arrived, when Dembele ran in behind and laid back for Forrest who found Rogic inside the box. The Australian, with typical poise, swivelled away from McCrorie and found the corner of the net with a smooth finish.

Rogic is a big talent who delivers on the big stage; he has now scored a goal in each of his three Old Firm appearances this season.

He had a better opportunity moments later, but fired straight at Wes Foderingham with Rangers looking increasingly ragged. They were being brutally ripped apart.

Callum McGregor scored Celtic's second goal with a clever, well-taken finish

Celtic's movement was impressive. They were determined and crisp in their passing. Scott Brown and Ntcham were allowed to stroll around midfield with quite startling ease.

They bossed this, and added a second when Kieran Tierney danced past Candeias and crossed towards Dembele.

Russell Martin's body shape was all wrong as he tried to intervene and he haplessly skewed the ball straight to McGregor, who finished emphatically beyond Foderingham.

At that point, it seemed an abacus might be required to keep count of the chances and goals Celtic might rack up.

Rangers defender Ross McCrorie was sent off for a foul on Celtic striker Moussa Dembele

Murty had to confront the reality of the situation, and he chose to replace Halliday before half-time. It was a horrible moment for the midfielder, but only added to the glee of the Celtic support.

That joy improved further after the break when McCrorie failed to cope with Dembele's power and pace, pulling the Celtic striker down in the box. It was a chastening afternoon for the young Rangers defender, who had no answer to Dembele's strength and guile.

McCrorie was ordered off before the Celtic striker cheekily dinked the spot kick away from Foderingham.

Rangers did improve for a spell, and had three glorious chances in succession. Two fell to Alfredo Morelos, the other to Bruno Alves from a corner, but Celtic goalkeeper Craig Gordon produced three wonderful stops.

Rangers' best chances fell to striker Alfredo Morelos, but he could not convert any of them

Celtic's threat eased a touch with the game over as a contest, but they still added a fourth when Rangers substitute Jason Holt clattered into Patrick Roberts inside the box.

Ntcham took this one, and confidently drilled home into the corner.

That put the seal on a thrilling afternoon for Celtic, who moved ever closer to the historic achievement of back-to-back trebles.

For Rangers, this was a bruising occasion. One that will leave them with lingering hurt and significant questions to answer.

Celtic's fourth goal came from the penalty spot after Jason Holt fouled Patrick Roberts