Question

if there is a triangle ABC with angle a,b,c respectively show that
cos b +c/2=sin a/2

Answer 1

$\huge \bf \color{seagreen} \: \star \: answer \: \star$

A,B and C are in arithmetic progression

⇒B=

$\frac{a + b}{2}$

⇒2B=A+C .......... (1)

A+B+C=180°

...... (2) [Property of triangle]

From (1) and (2), we get

B=60°

∴

$\frac{c}{a}$

sin2C+

a

c

sin2A=

sinC

sinA

2sinCcosC+

sinA

sinC

2sinAcosA

=2sinAcosC+2sinCcosA

=2sin(A+C)=2sinB=2×

2

3

=

3

Answer 2

Answer:

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