помогите

4sin x+5 cos x=x4

8sinx/2cosx/2+5cos²x/2-5sin²x/2-4sin²x/2-4cos²x/2=09sin²x/2-6sinx/2cosx/2-cos²x/2=0  /cos²x/2≠09tg²x/2-6tgx/2-1=0tgx/2=a9a²-6a-1=0D=36+36=72    √D=6√2a1=(6-6√2)/18=(1-√2)/3⇒tgx/2=arctg(1-√2)/3+πn⇒x=2arctg(1-√2)/3+2πna2=(6+6√2)/18=(1+√2)/3⇒tgx/2=arctg(1+√2)/3+πn⇒x=2arctg(1+√2)/3+2πn