5cos^2a+4cos^2β=4cosα则cos^2a+cos^2β

来源：学生作业帮助网 编辑：作业帮 时间：2024/11/24 03:32:02
5cos^2a+4cos^2β=4cosα则cos^2a+cos^2β
xSn0~ҤFõc {o1IְQqHT! Vq`@aQn+8hҮ||9nzݰA*Oø!2qrfyER#%-xEmJQ7|\i]Z;5Bp.3,I)Qj4mZ FMBX@՚O*e[o "Ler=0@Fi-$g 0 ԈWmbҖ|&1%qPڟ h\RsԠsΔ(1ΈD*^ ;)f@DV ؼ6'\r@z*S(ASY4ijI h+cA0U3 TC %?)są/,xCJP0[p \?Kњ,E' g^rasLipt:x[l3 g__y p٧7i6Lㅖ0g32=]J=D+'-z~x9?d oL_ 0?ۿH

5cos^2a+4cos^2β=4cosα则cos^2a+cos^2β
5cos^2a+4cos^2β=4cosα则cos^2a+cos^2β

5cos^2a+4cos^2β=4cosα则cos^2a+cos^2β
5cos^2a+4cos^2β=4cosα
令cosα = t
5t^2+4cos^2β=4t
4cos^2β=4t-5t^2
4cos^2β≥0
4t-5t^2≥0
5t^2-4t≤0
t(5t-4)≤0
0≤t≤4/5
5cos^2a+4cos^2β=4cosα
4cos^2a+4cos^2β=4cosα-cos^2α=4-4+4cosα-cos^2α=4-(2-cosα)^2=4-(2-t)^2
0≤t≤4/5
0≥ -t ≥ -4/5
2 ≥ 2-t ≥ 6/5
4 ≥ (2-t)^2 ≥ 36/25
-4≤-(2-t)^2≤-36/25
0≤4-(2-t)^2≤64/25
即0≤4cos^2a+4cos^2β≤64/25
0≤cos^2a+cos^2β≤16/25

5cos^2a+4cos^2β=4cosα>=0
4cos^2a+4cos^2β=4cosα-cos^2a=-[cosa-2]^2+4>=0
0<=cosa<=1
故cos^2a+cos^2β=(-[cosa-2]^2+4)/4=1-[cosa-2]^2
易知范围是[0,3]

-5/4到3/4闭区间

5cos^2a+4cos^2β=4cosα则cos^2a+cos^2β=
解析：∵5cos^2a+4cos^2β=4cosα>=0
4cos^2a+4cos^2β=4cosα-cos^2a=-[cosa-2]^2+4
∴cos^2a+cos^2β=-1/4[cosa-2]^2+1
∵0<=cosa<=1
令f(x)=1-1/4(x-2)^2 (0<=x<=1)
∴f(x)的值域，即cos^2a+cos^2β取值范围是[0,3/4]

5cos^2a+4cos^2β=4cosα则cos^2a+cos^2β 化简(1-sin^6 a-cos^6 a)/(cos^2 a-cos^4 a)== 5cos^2 α +4cos^2 β =4cosα,求cos^2 α +cos^2 β的取值范围? 已知5(cosα)^2+4(cosβ)^2=4cosα,则(cosα)^2+(cosβ)^2的取值范围是? sin^4+sin^2cos^2+cos^2a= cos (2 a/7）+cos(4 a/7)+cos(6 a/7)=? 计算：cos（π/5)+cos（2π/5)+cos(3π/5)+cos(4π/5) cos(pai/15)×cos(2pai/15)×cos(3pai/15)×cos(4pai/15)×cos(5pai/15)×cos(6pai/15)×cos(7pai/15)求值 cos(pai/15)×cos(2pai/15)×cos(3pai/15)×cos(4pai/15)×cos(5pai/15)×cos(6pai/15)×cos(7pai/15)求值 tan a =3求4sin a-2cos a/5cos+3sin a 求值:cos(π/11)cos(2π/11)cos(3π/11)cos(4π/11)cos(5π/11) 求值：cos(π/11)-cos(2π/11)+cos(3π/11)-cos(4π/11)+cos(5π/11) cos(π/11)cos(2π/11)cos(3π/11)cos(4π/11)cos(5π/11) 由cos(a+b)=cos a cos b-sin a sin b cos(a-b)=cos a cos b+sin a sin b解题设a为锐角,证：1、2分之根3乘cos a + 2分之1乘sin a=cos(6分之π-a)2、cos a-sin a=根号2cos(4分之π+a) 已知cos(a+b)=4/5,cos(a-b)=-4/5,3π/2 .已知Cos(a+b)=4/5,cos(a-b)= -4/5,3/2π 化简 1-sin^4a-cos^4a/cos^2a-cos^4a 一道算术题目↓↓x^2=5-4cosαx^2=25-24cosβcosα+cosβ=0 求X值