求证(9/a-4)+a>=10 a>4

求证(9/a-4)+a>=10 a>4 求证:a^4+1>=a^3+a 求证sin^4a+cos^4a=1 求证4cos(60-a)-cosacos(60+a)=cos3a sin∨4a-cos∨4a=sin²a-cos²a 求证 sin(2a)[cot(a/2)-tan(a/2)]=4cos^2(a)求证, 求证 3(1+a^3+a^4)>=(1+a+a^2)^2 a-2a+3a-4a+5a-6a+7a-8a+9a-10a+11a.+99a-100a= 求证:a 求证:|a| 求证3-sin^4a-cos^4a/2cos^a=1+tan^a+sin^a 速答 谢谢 已知a属于R,求证:3(1+a^2+a^4)>=(1+a+a^2)^2 求证sin^4a-cos^4a=-cos2a如题 求证 sin^4(a)-cos^4(a)=-cos(2a) a>0,b>0,a+b=1,求证1/2a+1+4/2b+1>=9/4 设㏒20^625=a,求证lg32=5（4-a)/4+a 求证：对于任意角a,cos^4a-sin^4a=cos2a 求证sin^4a+cos^4a=1-2sin^2acos^2a 求证2cos^2a+sin^4a=cos^4a+1