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Celtic through to Scottish Cup semi-final

Denayer, Griffiths, Commons and Van Dijk score for Celtic

Anthony Stokes and Ryan McGowan red carded

Both sides meet again in the league on Saturday

Celtic's dreams of a domestic treble remain intact after a comfortable Scottish Cup quarter-final replay win at home to Dundee United.

Jason Denayer headed Anthony Stokes' free-kick past Radoslaw Cierzniak in a one-sided first half.

Leigh Griffiths and Kris Commons added two more goals before Stokes was sent off for elbowing United's Paul Paton. Ryan McGowan was also dismissed for the visitors for a foul on Liam Henderson.

Virgil van Dijk added a fourth late on.

The score line reflected the flow of the game with United a pale shadow of the team that had held Celtic to a 1-1 draw in the first game at Tannadice.

Inverness Caledonian Thistle now await Celtic in a Hampden semi-final as they bid to add this trophy to last weekend's League Cup triumph, while Jackie McNamara has to pick his United players up for a return trip to Glasgow on Saturday, for the final game of four consecutive matches against Ronny Deila's side.

United could have been down to 10 men after a minute when goalkeeper Cierzniak brought down Griffiths just a few yards from the penalty box, and the Pole was perhaps fortunate to receive only a yellow card.

Celtic continued on the front foot. Griffiths directed Stokes' cross on target, though only into the arms of Cierzniak, but it was a warning shot and minutes later the home side were in the lead.

Stokes' curled delivery from a free-kick found Belgian centre-back Denayer, who powered home the header.

It was one attack after another for the home side and James Forrest and Griffiths both had numerous opportunities, with Van Dijk also threatening with a header.

Then Celtic hit the woodwork when Forrest beat John Rankin on the wing and sent over a cross which Cierzniak palmed against the crossbar.

Leigh Griffiths added the finishing touches to Scott Brown's long pass to make it 2-0 to Celtic

While there was only a goal in it though, United were still in the cup tie. McGowan's cut back from the byline was parried by Gordon and United forward Nadir Ciftci should have done better but did not realise the ball had landed just behind him.

Celtic defender Nir Bitton could have made it 2-0 when he was one-on-one with the goalkeeper, but he passed up his big chance.

United were more threatening in the opening minutes of the second half than they were for the whole of the first half, with McGowan and Ciftci both creating problems.

Just as they looked to be gaining some momentum, Griffiths volleyed Scott Brown's long pass into the net to give Celtic a second goal.

Cierzniak tipped a Stokes shot round the post, but United's resistance could not hold out and Commons played a one-two with John Guidetti before finding the back of the net.

Stokes and McGowan saw red within minutes of each other. Stokes for lashing out at Paton with an elbow, and the Australian followed him down the tunnel when he caught Liam Henderson with a hefty challenge.

Van Dijk combined with Denayer to add a fourth late on and wrap up the win.

Jason Denayer gets his head to Anthony Stokes' cross to make it 1-0

Kris Commons scored in between goals from Leigh Griffiths and Virgil van Dijk

Stokes was sent off for lashing out at Paul Paton.

Celtic players react angrily to a McGowan challenge on Liam Henderson, which saw the defender sent off