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\(cos^2\alpha=1-sin^2\alpha=1-\left(0,8\right)^2=0,36\)
\(\Rightarrow cos\alpha=0,6\)
\(1+cot^2\alpha=\dfrac{1}{sin^2\alpha}\Rightarrow cot^2\alpha=\dfrac{1}{sin^2\alpha}-1=\dfrac{9}{16}\)
\(\Rightarrow cot\alpha=0,75\)
\(tan\alpha=\dfrac{1}{cot\alpha}=\dfrac{1}{0,75}=\dfrac{4}{3}\)
\(\dfrac{1}{cos^2\alpha}=1+tan^2\alpha=1+\left(\dfrac{7}{24}\right)^2=\dfrac{625}{576}\)
\(\Rightarrow cos^2\alpha=\dfrac{576}{625}\)
\(cot\alpha=\dfrac{1}{tan\alpha}=\dfrac{24}{7}\)
\(1+tan^2\alpha=\dfrac{1}{cos^2\alpha}\Rightarrow cos^2\alpha=\dfrac{576}{625}\Rightarrow cos\alpha=\dfrac{24}{25}\)
\(1+cot^2\alpha=\dfrac{1}{sin^2\alpha}\Rightarrow sin^2\alpha=\dfrac{49}{625}\Rightarrow cos\alpha=\dfrac{7}{25}\)
a) khai triển được 2sin2+2cos2=2(sin2+cos2=2.1=2
b)cot2-cos2.cot2=cot2(1-cos2)=cot2.sin2=cos2/sin2.sin2=cos2
c)sin.cos(tan+cot)=sin.cos.tan+sin.cos.cot=sin.cos.sin/cos+sin.cos.cos/sin=sin2+cos2=1
d)tan2-tan2.sin2=tan2(1-sin2)=tan2.cos2=sin2/cos2.cos2=sin2
cos α = 0.96
tan α = 0.291
cot α = 3.42
cos α = 0.96 tan α ≈ 0.3 cot α ≈ 3
ta có
sin2α + cos2α =1
ts : (0.28)2+cos2α =1 ↔cos2α = 576/625 ↔cosα =24/25
mà : tanα = sinα/cosα
ts: tanα=7/25/24/25=7/24 ⇒cotα = 24/7
cos a = 0.96
tan a = 0.291
cot a = 3.42
sin a= 0,96
tan a=7/24
cot a=24/7
cos a = 0,96
tan a = 7/24
cot a = 24/7
cos a =0,96
tan a =\(\dfrac{7}{24}\)
cot a=\(\dfrac{24}{7}\)
Cos a = 0,96
Tan a = 7/24
Cot a = 24/7
cos a=0,96
tan a=7/24
cot a=24/7
+ sin2a + cos2a = 1 mà sin a =0,28
=>(0,28)2 + cos2a=1
=>0,0784+cos2a = 1
=>cos2a = 1- 0.0784=0,9216
=>cos a = 0,96
+ tan a = sin a/cos a = 0,28/0,96=7/24
+ cot a . tan a=1 mà tan a = 7/24
=>cot a . 7/24 =1
=>cot a =24/7
+)sin2a+cos2a=1có sin a=0,28
=>(0,28)2+cos2a=1
=>cos a=0,96
+)tan a = sin a /cos a có cos a=0,96,sin a=0,28
=>tan a=7/24
+)cot a . tan a=1 có tan a=7/24
=>cot a=24/7
cos α= 0,96
tan α=7/24
cot α=24/7
cos a = \(\dfrac{24}{25}\)
tan a = \(\dfrac{7}{24}\)
cot a =\(\dfrac{24}{7}\)
cos a = 0,96
tan a= 7/24
cotg a= 24/7
-cos a=0,96 -tan a=7/24 -cot a=24/7
cos a = 0.98
tan a = 0.291
cot a = 3.42
\(\sin^2a+\cos^2a=1\Rightarrow\sqrt{1-\sin^2a=\sqrt{1-(}0.28)^2=0.96}\)
+) \sin^2\alpha+\cos^2\alpha=1\Rightarrow\cos\alpha=\sqrt{1-\sin^2\alpha}=\sqrt{1-\left(0,28\right)^2}=0,96.sin2α+cos2α=1⇒cosα=1−sin2α=1−(0,28)2=0,96.
+) \tan\alpha=\dfrac{\sin\alpha}{\cos\alpha}=\dfrac{0,28}{0,96}=\dfrac{7}{24}.tanα=cosαsinα=0,960,28=247.
+) \cot\alpha.\tan\alpha=1\Rightarrow\cot\alpha=\dfrac{24}{7}.cotα.tanα=1⇒cotα=724.
\(+)sin^2a+cos^2a=1\Rightarrow cos^{^{ }}a=\sqrt{1-sin^2a}=\sqrt[]{1-\left(0,28\right)^2=0,96}\)
\(+)tan^{ }a=\dfrac{sin^{ }a}{cos^{ }a}=\dfrac{0,28}{0,96}=\dfrac{7}{24}\)
\(+)cot^{ }a.tan^{ }a=1\Rightarrow cot^{ }a=\dfrac{24}{7}\)