Cómo hacer la octava pregunta del examen de ingreso a la universidad de matemáticas

tana=(1 sinb)/cosb

=(sin^2 b/2 2 sinb/2 cosb/2 cos^2 b/2)/(cos^2 b/2 -sin^2 b /2)

=(cosb/2 sinb/2)^2/(cos^2 b/2 -sin^2 b/2)

=(cosb/2 sinb /2)/(cosb/2-sinb/2)

= cosb/2(1 tanb/2)/cosb/2(1-tanb/2)

=( 1 tanb/2)/(1-tanb/2)

=(tan 45 tanb/2)/(1-tan 45 tanb/2)

=tan(45 b /2)

∴a=45 b/2

2a-b=90

Elija b.