2-cos8x-cos6x+cos4x-cos2x=0

Đặt  \(\frac{a}{2}=\frac{b}{5}=\frac{c}{7}=k\), ta được \(a=2k;b=5k;c=7k\)Ta có:

\(\frac{2k-5k+7k}{2k+2.5k-7k}=\frac{4k}{2k+10k-7k}=\frac{4k}{5k}=\frac{4}{5}\)

\(\Rightarrow A=\frac{4}{5}\)

cos2x-sin3x+cos5x=sin10x+8cosx

sin5x+sin3x+2cos2=1+sin4x

tìm GTNN của hàm số

y=3(sinx-cosx)+4sinxcosx \(\forall x\in\left\{\frac{-\Pi}{2};0\right\}\)

\(0\le\frac{1}{2}arccos\left(\frac{5}{7}\right)+k\Pi\le2\Pi\)

tìm k

cho pt \(\sqrt{3}sin2x-2cos^2x-m=0\) tìm m thỏa mãn pt có nghiệm x\(\in\left[\frac{\Pi}{4};\frac{5\Pi}{12}\right]\)

1 nghiem cua phuong trinh : \(sin^42x+cos^42x=1\) la

1 nghiem cua phuong trinh : \(sin^42x+cos^4x=1\) la

A=a+b-5

B=-b-c+1

C=b-c-4

D=b-a

A+B=a+b-5+(-b-c+1)

A+B=a+b-5-b-c+1

A+B=(b-b)+a-c-(5+1)

A+B=0+a-c-4

A+B=a-c-4

C-D=b-c-4-(b-a)

C-D=b-c-4-b+a

C-D=(b-b)+a-c-4

C-D=0+a-c-4

C-D=a-c-4

Vì a-c-4=a-c-4 nên A+B=C-D

Vậy A+B=C-D=a-c-4