Given α, β ∈ [0, π), Tan α / 2 = 2 / 3, cos (α + β) = 5 / 13, find cos β

Given α, β ∈ [0, π), Tan α / 2 = 2 / 3, cos (α + β) = 5 / 13, find cos β

From Tan (α / 2) = 2 / 3, sin 2 (A / 2) / cos 2 (A / 2) = 4 / 9 is obtained, and sin (A / 2) = 4 / 13, cos 2 (A / 2) = 9 / 13, so cosa = 5 / 13 > 0, ν Sina = 12 / 13, cos (α + β) = 5 / 13, α, β∈ [0, π)] sin (α + β) = 12 / 13, cos β = (α +...)

How to input degree, minute and second in scientific calculator

Input the number directly and press the "," key in the corresponding position

How to use the length of the edge to find the degree of the angle, on the calculator

Those that are not triangles can be divided into triangles
The cosine theorem is generally available
The most simple right triangle can be arctangent function

How to set up a calculator to convert degrees into radians

First input the angle value in degrees, minutes and seconds, press the equal key, and then press the degree key!

How to press Tan square with a calculator How to press Tan square sin square cos square with a calculator Is Tan square (Tan a) square?

tan²α=(tanα)²,
First calculate Tan α, and then square the result
For example:
tan²45°=(tan45°)²=1²=1,

Tan (a + b) =? Please expand（

This is the formula of two angles and tangent
If you don't remember, it can be deduced from the formula of two angles and sine and the formula of two angles and cosine
tan(A+B)=sin(A+B)/cos(A+B)=[sinAcosB+cosAsinB]/[cosAcosB-sinAsinB]
Divide the numerator and denominator by cosacosb
tan(A+B)=(tanA+tanB)/(1-tanAtanB)

How does Tan α = - Tan (π - α) come out?

∵ the period of Tan α is π, where α is regarded as an acute angle,
∴π-α>90°
∴tan(π-α)

Tanα/2

tana/2=sina/2 / cosa/2
=2sina/2*cosa/2 / 2cos^2a/2
=sina/(1+cosa)
tana/2=sina/2 / cosa/2
=2sin^2a/2 /2sina/2cosa/2
=(1-cosa)/sina

(maths)tan(a+b)=? tan(a+b)=? How are formulas derived?

Tan (a + b) = sin (a + b) / cos (a + b) = (sinacosb + cosasinb) / (cosacosb sinasinb) is divided by cosacosb (COSA is not equal to 0, CoSb is not equal to 0) Tan (a + b) = (Tana + tanb) / (1-tanatanb) if Tan (a-b), then Tan (a-b) = (Tana tanb) / (1 + tanatanb)

Why is Tan 45 equal to 1.619775191?

The format is wrong. You're in radians
Identification completed