作业帮已知tana=-1/3求sin²a+3sinacosa-1的值
来源：学生作业帮助网 编辑：作业帮 时间：2024/11/05 18:54:36
x){}KKmu
ml*SS64N6u
jyڰ&HT-v6dW 恔 tlA`>3a!X: IC !d}C41dlrHVdu-ͅs,Mm @ T
已知tana=-1/3求sin²a+3sinacosa-1的值
已知tana=-1/3求sin²a+3sinacosa-1的值
已知tana=-1/3求sin²a+3sinacosa-1的值
tana=-1/3
sina/cosa=-1/3
-3sina=cosa
cos²a+sin²a=1
9sin²a+sin²a=1
10sin²a=1
sin²a=1/10
sin²a+3sinacosa-1
=sin²a-9sin²a-1
=-8sin²a-1
=-8/10-1
=-9/5