Question

高中数学，第5题，求解

Answer 1

cos^2 1°+cos^2 2°+cos^2 3°+...+cos^2 90°
=(cos^21^+cos^2 89°)+(cos^2 2°+cos^2 88°)+...+(cos^2 44°+cos^2 46°)+cos^2 45°
=(cos^21^+sin^2 1°)+(cos^2 2°+sin^2 2°)+...+(cos^2 44°+sin^2 44°)+1/2
=44+1/2
=89/2

Answer 2

cos^1°+cos^2°+cos^3°+……+cos^89°+cos^90°
=cos^1°+cos^2°+cos^3°+……+sin^3°+sin^2°+sin^1°+0
=cos^1°+sin^1°+cos^2°+sin^2°+cos^3°+sin^3°+……+cos^44°+sin^44°+cos^45°
=1+1+1+……+1+1/2
=44.5