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cos ( α − β ) " role="presentation" style="box-sizing: content-box; -webkit-tap-highlight-color: rgba(0, 0, 0, 0); margin: 0px; padding: 5px 2px; display: inline-block; line-height: 0; overflow-wrap: normal; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; color: rgb(51, 51, 51); font-family: "Microsoft YaHei", arial, SimSun, sans-serif, tahoma; background-color: rgb(255, 255, 255); position: relative;"> cos ( α − β )