求证：cos(n-1)AcosA-cosnA = sin(n-1)AsinA .还有已知sin( A + 24°) = sin(_数学解答

求证：cos(n-1)AcosA-cosnA = sin(n-1)AsinA .
还有已知sin( A + 24°) = sin( A + 66°)，求tanA的值。

人气：386 ℃　时间：2020-10-01 23:34:19

解答

cosna=cos[（n-1）a+a]=cos(n-1)acosa-sin(n-1)acsinacos(n-1)acosa-cosna=cos(n-1)acosa-{cos(n-1)acosa-sin(n-1)acsina}=sin(n-1)acsina sin(A+66)=sin(A+24) sin(A+66)-sin(A+24)=0 2cos(A+45)sin21=0,(sin21≠0)...