已知sin(30°+ A )=3/5 ,60°
问题描述:
已知sin(30°+ A )=3/5 ,60°
数学人气:411 ℃时间:2020-07-04 12:47:49
优质解答
(1/2)cosA+(√3/2)sinA=3/5
5cosA+5√3sinA=6
5√3√(1-cos^2A)=6-5cosA
75(1-cos^2A)=36+25cos^2A-60cosA
50cos^2A-60cosA-39=0
cosA=[6-√114]/10
5cosA+5√3sinA=6
5√3√(1-cos^2A)=6-5cosA
75(1-cos^2A)=36+25cos^2A-60cosA
50cos^2A-60cosA-39=0
cosA=[6-√114]/10
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答
(1/2)cosA+(√3/2)sinA=3/5
5cosA+5√3sinA=6
5√3√(1-cos^2A)=6-5cosA
75(1-cos^2A)=36+25cos^2A-60cosA
50cos^2A-60cosA-39=0
cosA=[6-√114]/10