cos(a+b)=cosacosb-sinasinb
cos(a-b)=cosacosb+sinasinb
所以或银有,2cosacosb=0.2+0.6
2sinasinb=0.6-0.2
tana*tanb=(2sinasinb)/氏团陆歼顷(2cosacosb)=0.5
如题有:
cosa+b) = cosacosb-sinasinb=0.2
cos(a-b) = cosacosb+sinasinb=0.6
两式联局谨立有,
cosacosb=0.4
sinasinb=0.2
而基腊拦搏胡tana X tanb=(sina/cosa)X (sinb/cosb)=(sinasinb)/(cosacosb)=0.2/0.4=0.5
cos(a+b)= cosacosb-sinasinb
cos(a-b)=cosacosb+sinasinb
,2cosacosb=0.2+0.6
2sinasinb=0.6-0.2
tanaXtanb=(2sinasinb)/(2cosacosb)=0.5
cosacosb-sinasinb=0.2 cosacosb+sinasinb=0.6 cosacosb=0.4 sinasinb=0.2
tanaxtanb=sinasinb/cosacosb=0.2/棚歼0.4=0.5
tana a=60 sina=√3/链核冲2 cosa=1/氏数2
cos(a+b)=cosacosb-sinasinb=0.2
cos(a-b)=cosacosb+sinasinb=0.6
cosacosb=0.4
sinasinb=0.2
tana X tanb=0.5
解答:
(1)设兔子有x只,则:鸡有(x+15)只
所以:4x+2(x+15)=132,解得:x=17
所以:有兔子17只,鸡32只
(2)三人一共得分为74+22+87=183
设三人共答对了携银x题,则:三人没有答对的题为(30-x)
则:183=10x-3(30-x),解滑慎得:x=21
答:三信隐敬个人共做对了21个题