2b=a+c

sine law

2sinB=sinA+sinC

A-C=90

A=90 degrees+Celsius

∴A is an obtuse angle and C is an acute angle.

2sinB=sinA+sinC

2sin(A+C)=sinA+sinC

2sin(90 +2C)=sin(90 +C)+sinC

2cos2C=cosC+sinC

2(cos？ Sin. C)=cosC+sinC

2(cosC+sinC)(cosC-sinC)= cosC+sinC

∴cosC-sinC= 1/2

Crime of combination? C+cos？ C= 1

SinC=(√7- 1)/4。

Everything else is fine.

Sina.com

=sin(C+90)

=cosC

=sinC+ 1/2

=(√ 7+ 1)/4

Simbe

=√7/4

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