作业帮高一数学,13.14.15题,急!
来源：学生作业帮 编辑：作业帮 分类：数学作业 时间：2024/04/26 04:13:18
高一数学,13.14.15题,急!
13.1/2-cos(2A+π/2)/2+1/2-cos(2A-π/2)/2=1+(sin2A-sin2A)/2=1；
14.sin²1°=(1-cos2°)/2,sin²89°=[1-cos(π-2°)]/2,sin²2°=(1-cos4°)/2,sin²88°=[1-cos(π-4°)]/2,┈┈sin²44°=(1-cos88°)/2,sin²46°=[1-cos(π-88°)]/2,sin²45°=1/2,原式=sin²1°+sin²89°+sin²2°+sin²88°+┈┈sin²44°+sin²46°+1/2=1+1+┈┈1+1/2=44+1/2=89/2；
15.在π/4
14.sin²1°=(1-cos2°)/2,sin²89°=[1-cos(π-2°)]/2,sin²2°=(1-cos4°)/2,sin²88°=[1-cos(π-4°)]/2,┈┈sin²44°=(1-cos88°)/2,sin²46°=[1-cos(π-88°)]/2,sin²45°=1/2,原式=sin²1°+sin²89°+sin²2°+sin²88°+┈┈sin²44°+sin²46°+1/2=1+1+┈┈1+1/2=44+1/2=89/2；
15.在π/4