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∵△ABC中,sinA:sinB:sinC=2:3:4,∴根據正弦定理,得a:b:c=2:3:4,可得c為最大邊,角C是最大角設a=2k,b=3k,c=3k(k>0)∴cosC=a2+b2−c22ab=4k2+9k2−16k22×2k×3k=-14即最大角的余弦值為-14故答案為:-14
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