表达式4: 0 equals tangent left parenthesis, "a" , right parenthesis minus StartFraction, 9.8 1 "x" Over 2 "v" squared cos squared left parenthesis, "a" , right parenthesis , EndFraction0=tana−9.81x2v20cos2a
4
表达式5: "y" equals StartFraction, tan left parenthesis, "x" , right parenthesis times 2 "v" squared times cos squared left parenthesis, "x" , right parenthesis Over 9.8 1 , EndFraction left brace, 0 less than or equal to "x" less than or equal to 90 , right bracey=tanx·2v20·cos2x9.810≤x≤90