已知派/4<α<3派/40<β<派/4cos(派/4-α)=3/5sin(3派/4+β)=5/13求sin(α+β)要過程謝謝

熱心網(wǎng)友

已知π/4<α<3π/40<β<π/4cos(π/4-α)=3/5sin(3π/4+β)=5/13求sin(α+β)解cos(π/4-α)=cos(α-π/4)=3/5sin(α-π/4)=4/5 (因π/4<α<3π/4）sin(3π/4+β)=sin[π-(π/4-β)]=sin(π/4-β)即sin(π/4-β)=5/13cos(π/4-β)=12/13 (因0<β<π/4）所以sin(α+β)=sin[(α-π/4)-(π/4-β)]=sin(α-π/4)cos(π/4-β)-cos(α-π/4)sin(π/4-β)=(4/5)(12/13)-(3/5)(5/13)=33/65

熱心網(wǎng)友

太簡當了！！！你沒學數(shù)學 啊