\(D=\dfrac{sin\alpha+cos\alpha}{sin\alpha-cos\alpha}=\dfrac{sin\alpha+cos\alpha}{sin\alpha}:\dfrac{sin\alpha-cos\alpha}{sin\alpha}=\left(1+cot\alpha\right):\left(1-cot\alpha\right)=\left(1+\dfrac{4}{3}\right):\left(1-\dfrac{4}{3}\right)=-7\)
Biết cot α=\(\sqrt{5}\). Tính giá trị biểu thức: A=\(\dfrac{\sin^2\alpha+\cos^2\alpha}{\sin\alpha.\cos\alpha}\)
CMR:\(1,\tan\alpha\cdot\cot\alpha=1\)
\(2,\sin^2\alpha+\cos^2\alpha=1\)
\(3,\tan\alpha=\dfrac{\sin\alpha}{\cos\alpha};\cot\alpha=\dfrac{\cos\alpha}{\tan\alpha}\)
Cho \(tan\alpha=\dfrac{7}{24}\)Tính \(sin\alpha,cos\alpha,cot\alpha\)
Biết \(tan\alpha=2.\) Tính \(\dfrac{sin\alpha+cos\alpha}{sin\alpha-cos\alpha}\)
Giúp mình vs chiều phải nộp bài rồi
a)C= \(4\cos^2\alpha-3\sin^2\alpha.cos=\frac{4}{7}\)
b)\(\cos^2\alpha+\cos^2\beta+\cos^2\alpha.\sin^2\beta+\sin^2\alpha\)
c)2\(\left(\sin\alpha-\cos\alpha\right)^2-\left(\sin\alpha+\cos\alpha\right)^2+\left(\sin\alpha.\cos\alpha\right)\)
d)\(\left(\tan\alpha-\cot\alpha\right)^2-\left(\sin\alpha+\cot\alpha\right)^2\)
Chứng minh rằng: \(\dfrac{\sin\alpha+\cos\alpha-1}{1-\cos\alpha}\)=\(\dfrac{2\cdot\cos\alpha}{\sin\alpha-\cos\alpha+1}\)
Cho \(sin\alpha=0,8\). Tính \(cos\alpha,tan\alpha,cot\alpha\)
Cho \(sin\alpha+cos\alpha=\dfrac{7}{5}\). Tính \(tan\alpha\)
A = \(58\sin^6\alpha-87\sin^4\alpha+58\cos^6\alpha-87\cos^4\alpha\)
B = \(\left(\sin\alpha+\cos\alpha\right)^2-2\sin.\cos\alpha+3\)
