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If


if \: \tan( \beta + \alpha ) - (3 + 2 √(2) ) \tan( \beta ) = \: 0 \: \\: show \: that \: \sin(2 \beta + \alpha ) = √(2) \sin( \alpha )
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User Joao Polo
by
6.5k points

1 Answer

1 vote

Explanation:

tan(β+α) − (3+2√2) tan β = 0

Convert to sine and cosine:

sin(β+α) / cos(β+α) − (3+2√2) sin β / cos β = 0

sin(β+α) / cos(β+α) = (3+2√2) sin β / cos β

Cross multiply:

sin(β+α) cos β = (3+2√2) sin β cos(β+α)

sin(2β+α)

Rearrange:

sin(β+(β+α))

Angle sum formula:

sin β cos(β+α) + sin(β+α) cos β

Substitute:

sin β cos(β+α) + (3+2√2) sin β cos(β+α)

(4+2√2) sin β cos(β+α)

Rearrange:

(2+√2) (2 sin β cos(β+α))

Product to sum:

(2+√2) (sin(2β+α) + sin(-α))

Reflection:

(2+√2) (sin(2β+α) − sin α)

Since this equals sin(2β+α) from the beginning:

(2+√2) (sin(2β+α) − sin α) = sin(2β+α)

(2+√2) sin(2β+α) − (2+√2) sin α = sin(2β+α)

(1+√2) sin(2β+α) − (2+√2) sin α = 0

(1+√2) sin(2β+α) = (2+√2) sin α

sin(2β+α) = (2+√2) / (1+√2) sin α

Multiply by the conjugate:

sin(2β+α) = (2+√2)(1−√2) / ((1+√2)(1−√2)) sin α

sin(2β+α) = (2−2√2+√2−2) / (1−√2+√2−2) sin α

sin(2β+α) = (-√2) / (-1) sin α

sin(2β+α) = √2 sin α

User Martin Cazares
by
6.1k points
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