① 楂樻暟姹傛瀬闄愭眰澶х炲憡璇夋垜鎴戝摢閲岄敊浜嗭纴鎴戠殑绛旀堟槸1锛屾ｇ‘绛旀堟槸2锛
搴旇ヨ佸啀鐢ㄤ竴娆℃礇蹇呰揪娉曞垯lim (1/cos^2x - 1/(1+x^2))/(1-cosx)鍒嗗瓙鍒嗘瘝閮借秼杩戜簬0锛岀敤娲涘繀杈炬硶鍒欙纴鍒嗗瓙鍒嗘瘝鍒嗗埆姹傚涓婂纺 = lim (2sinx/cos^3x + 2x/(1+x^2)^2)/ sinx= lin (2/cos^3x + 2x/sinx / (1+x^2)^2)= 4