三角函数大题 球解析3.在△ABC中,角A,B,C,所对的边分别为a,b,c,且cosC=1/5.(1)求sin(C+π/4)的值(2)若CA弧乘CB弧=1,a+b=√37,求边c的值及△ABC的面积.4.在△ABC中,角A,B,C的对边分别为a,b,c,满足a^2+c^2-b^2=ac.(1
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![三角函数大题 球解析3.在△ABC中,角A,B,C,所对的边分别为a,b,c,且cosC=1/5.(1)求sin(C+π/4)的值(2)若CA弧乘CB弧=1,a+b=√37,求边c的值及△ABC的面积.4.在△ABC中,角A,B,C的对边分别为a,b,c,满足a^2+c^2-b^2=ac.(1](/uploads/image/z/15074992-64-2.jpg?t=%E4%B8%89%E8%A7%92%E5%87%BD%E6%95%B0%E5%A4%A7%E9%A2%98+%E7%90%83%E8%A7%A3%E6%9E%903.%E5%9C%A8%E2%96%B3ABC%E4%B8%AD%2C%E8%A7%92A%2CB%2CC%2C%E6%89%80%E5%AF%B9%E7%9A%84%E8%BE%B9%E5%88%86%E5%88%AB%E4%B8%BAa%2Cb%2Cc%2C%E4%B8%94cosC%3D1%2F5.%281%29%E6%B1%82sin%28C%2B%CF%80%2F4%29%E7%9A%84%E5%80%BC%EF%BC%882%29%E8%8B%A5CA%E5%BC%A7%E4%B9%98CB%E5%BC%A7%3D1%2Ca%2Bb%3D%E2%88%9A37%2C%E6%B1%82%E8%BE%B9c%E7%9A%84%E5%80%BC%E5%8F%8A%E2%96%B3ABC%E7%9A%84%E9%9D%A2%E7%A7%AF.4.%E5%9C%A8%E2%96%B3ABC%E4%B8%AD%2C%E8%A7%92A%2CB%2CC%E7%9A%84%E5%AF%B9%E8%BE%B9%E5%88%86%E5%88%AB%E4%B8%BAa%2Cb%2Cc%2C%E6%BB%A1%E8%B6%B3a%5E2%2Bc%5E2-b%5E2%3Dac.%281)
三角函数大题 球解析3.在△ABC中,角A,B,C,所对的边分别为a,b,c,且cosC=1/5.(1)求sin(C+π/4)的值(2)若CA弧乘CB弧=1,a+b=√37,求边c的值及△ABC的面积.4.在△ABC中,角A,B,C的对边分别为a,b,c,满足a^2+c^2-b^2=ac.(1
三角函数大题 球解析
3.在△ABC中,角A,B,C,所对的边分别为a,b,c,且cosC=1/5.
(1)求sin(C+π/4)的值
(2)若CA弧乘CB弧=1,a+b=√37,求边c的值及△ABC的面积.
4.在△ABC中,角A,B,C的对边分别为a,b,c,满足a^2+c^2-b^2=ac.
(1)求角B的大小
(2)设m=(sinA,cos2A),B=(-6,-1),求m×N的最小值.
5.在△ABC中,已知sin(A+B)=sinB+sin(A-B).
(1)求角A;
(2)若|BC|弧=7,AB弧乘AC弧=20,求|AB弧+AC弧|.
三角函数大题 球解析3.在△ABC中,角A,B,C,所对的边分别为a,b,c,且cosC=1/5.(1)求sin(C+π/4)的值(2)若CA弧乘CB弧=1,a+b=√37,求边c的值及△ABC的面积.4.在△ABC中,角A,B,C的对边分别为a,b,c,满足a^2+c^2-b^2=ac.(1
3.在△ABC中,角A,B,C,所对的边分别为a,b,c,且cosC=1/5.
(1)求sin(C+π/4)的值
(2)若CA弧乘CB弧=1,a+b=√37,求边c的值及△ABC的面积.
sin(c+45')=sinc*cos45'+cosc*sin45'
(sinc)^2+(cosc)^2=1,cosc=1/5
自己代人计算
4.在△ABC中,角A,B,C的对边分别为a,b,c,满足a^2+c^2-b^2=ac.
(1)求角B的大小
(2)设m=(sinA,cos2A),B=(-6,-1),求m×N的最小值.
(1)由余弦定理知
b^2=a^2+c^2-2ac*cosB
又a^2+c^2-b^2=ac,得
2ac*cosB=ac
所以cosB=1/2
所以B=pi/3
(2) M.N = -6sinA-cos2A
= -6sinA-[1-2(sinA)^2]
= 2(sinA)^2-6sinA-1
令 t=sinA 因为 A>0,且 A