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The Ivorian could have doubled Arsenal's lead in the 15th minute when he found himself at the end of a Bacary Sagna cross inside the Reading penalty area, but failed to keep his header on target.
Arsene Wenger's side then had a penalty appeal turned down when Giroud went down under Taylor's challenge, before Gervinho failed to finish a move he himself created with pace and control.
Arsenal dominated the remainder of the first half, Aaron Ramsey, Cazorla and Gervinho all coming close to consolidating their lead.
The start of the second period saw the London club double their advantage through Cazorla, who curled an effort from the edge of the Reading 18-yard box into the net.
Giroud made it 3-0 to Arsenal midway through the second half following a counter-attacking move that had Gervinho at its heart.
Moments later Hal Robson-Kanu pulled one back for Reading, but Mikel Arteta secured the points for the hosts with a penalty on 76 minutes that Adrian Mariappa conceded after bringing down Alex Oxlade-Chamberlain.