求值：tan5º+cot5º+2sec80º如上.

求值：tan5º+cot5º+2sec80º如上.
求值：tan5º+cot5º+2sec80º
如上.

求值：tan5º+cot5º+2sec80º如上.
tan5º+cot5º-2sec80º
=sin5/cos5+cos5/sin5-2/sin10
=[(sin5)^2+(cos5)^2-1]/sin5cos5
=(1-1)/sin5cos5
=0