用高一知识解已知角a的终边过点P(-3t,4t)(t∈R,t≠0),求角a的正弦、余弦和正切值

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用高一知识解已知角a的终边过点P(-3t,4t)(t∈R,t≠0),求角a的正弦、余弦和正切值
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用高一知识解已知角a的终边过点P(-3t,4t)(t∈R,t≠0),求角a的正弦、余弦和正切值
用高一知识解已知角a的终边过点P(-3t,4t)(t∈R,t≠0),求角a的正弦、余弦和正切值

用高一知识解已知角a的终边过点P(-3t,4t)(t∈R,t≠0),求角a的正弦、余弦和正切值
a的终边经过点P(-3t,4t)(t不等于0);
∴t>0时,P在第二象限;
sina=4t/5t=4/5;
cosa=-3t/5t=-3/5;
tana=-3t/4t=-3/4;
t<0时,P在第四象限;
sina=4t/(-5t)=-4/5;
cosa=-3t/(-5t)=3/5;
tana=-3t/4t=-3/4;

r^2=(-3t)^2+(4t)^2=(5t)^2
当t>0时,|r|=5t,则
sin a = 4t/5t = 4/5
cos a = (-3t)/5t = -3/5
tan a = 4t/(-3t) = -4/3
当t<0时,|r|=-5t,则
sin a = -4/5
cos a = 3/5
tan a = 4/3
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