若tan(2pai-a)=根号5/2,且a属于(-pai/2,0),sin(pai+a)=?坐等因为tan(2pai-a)=tan(-a)=-tan(a)=根号5/2 tan(a)=负根号5/2 sin(pai+a)=-sin(a) sin(a)=根号5/3所以sin(pai+a)=-根号5/3怎么得到的sin(a)=根号5/3
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![若tan(2pai-a)=根号5/2,且a属于(-pai/2,0),sin(pai+a)=?坐等因为tan(2pai-a)=tan(-a)=-tan(a)=根号5/2 tan(a)=负根号5/2 sin(pai+a)=-sin(a) sin(a)=根号5/3所以sin(pai+a)=-根号5/3怎么得到的sin(a)=根号5/3](/uploads/image/z/7080594-42-4.jpg?t=%E8%8B%A5tan%282pai-a%29%3D%E6%A0%B9%E5%8F%B75%2F2%2C%E4%B8%94a%E5%B1%9E%E4%BA%8E%28-pai%2F2%2C0%29%2Csin%28pai%2Ba%29%3D%3F%E5%9D%90%E7%AD%89%E5%9B%A0%E4%B8%BAtan%282pai-a%29%3Dtan%EF%BC%88-a%EF%BC%89%3D-tan%EF%BC%88a%EF%BC%89%3D%E6%A0%B9%E5%8F%B75%2F2+tan%EF%BC%88a%EF%BC%89%3D%E8%B4%9F%E6%A0%B9%E5%8F%B75%2F2+sin%28pai%2Ba%29%3D-sin%EF%BC%88a%EF%BC%89+sin%EF%BC%88a%EF%BC%89%3D%E6%A0%B9%E5%8F%B75%2F3%E6%89%80%E4%BB%A5sin%28pai%2Ba%29%3D-%E6%A0%B9%E5%8F%B75%2F3%E6%80%8E%E4%B9%88%E5%BE%97%E5%88%B0%E7%9A%84sin%EF%BC%88a%EF%BC%89%3D%E6%A0%B9%E5%8F%B75%2F3)
若tan(2pai-a)=根号5/2,且a属于(-pai/2,0),sin(pai+a)=?坐等因为tan(2pai-a)=tan(-a)=-tan(a)=根号5/2 tan(a)=负根号5/2 sin(pai+a)=-sin(a) sin(a)=根号5/3所以sin(pai+a)=-根号5/3怎么得到的sin(a)=根号5/3
若tan(2pai-a)=根号5/2,且a属于(-pai/2,0),sin(pai+a)=?坐等
因为tan(2pai-a)=tan(-a)=-tan(a)=根号5/2 tan(a)=负根号5/2 sin(pai+a)=-sin(a) sin(a)=根号5/3所以sin(pai+a)=-根号5/3
怎么得到的sin(a)=根号5/3
若tan(2pai-a)=根号5/2,且a属于(-pai/2,0),sin(pai+a)=?坐等因为tan(2pai-a)=tan(-a)=-tan(a)=根号5/2 tan(a)=负根号5/2 sin(pai+a)=-sin(a) sin(a)=根号5/3所以sin(pai+a)=-根号5/3怎么得到的sin(a)=根号5/3
∵a属于(-π/2,0)
∴sina-tana=√5/2
==>tana=-√5/2
==>sina/cosa=-√5/2
==>sina=-(√5/2)cosa
==>(-(√5/2)cosa)²+cos²a=1 (∵sin²a+cos²a=1)
==>(9/4)cos²a=1
==>cos²a=4/9
∴sina=-√(1-cos²a)=-√(1-(4/9)²)=-√5/3
故sin(π+a)=-sina=-(-√5/3)=√5/3.