trig help

The question is solve sinθtanθ+2sinθ=3cosθ
What ive done is replace the tanθ with sinθ/cosθ to give 2sinθ/cosθ+2sinθ=3cosθ
which i simplified to 2tanθ + 2sinθ=3cosθ
then rearranged the sin and cos to get 2tanθ+ sinθ/cosθ =3/2
which i simplified to 3tanθ=3/2
then rearranged to tanθ=1/2
however this only gives one answer for the range 0<θ<180 so idk if it is right?

Reply 1

Skiwi

13

Its gone wrong in the first line, changing sin(theta)tan(theta) would give sin^2(theta)/cos(theta)
Because in the original expression you are multiplying sin and tan, when you apply the identity you are multiplying sin and sin/cos

(edited 2 years ago)

Reply 2

XITounsi841

11

Original post by selugawi

The question is solve sinθtanθ+2sinθ=3cosθ
What ive done is replace the tanθ with sinθ/cosθ to give 2sinθ/cosθ+2sinθ=3cosθ
which i simplified to 2tanθ + 2sinθ=3cosθ
then rearranged the sin and cos to get 2tanθ+ sinθ/cosθ =3/2
which i simplified to 3tanθ=3/2
then rearranged to tanθ=1/2
however this only gives one answer for the range 0<θ<180 so idk if it is right?

Just divide everything by cos

Reply 3

Penginium

6

Hey, that's the exact same Q's that came up on my end of term assessment.

trig help

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you