Solving trigonometric equations: do I need to consider different cases in this example? I'm trying to solve this set of trigonometric equations: tan((delta+beta)/(2)) = c* tan((theta)/(2)) b* tan((delta- beta)/(2)) = a cos ((delta+ beta)/(2)) cos((gamma)/(2)) = cos((theta)/(2))

Rihanna Bentley

Rihanna Bentley

Answered question

2022-11-18

Solving trigonometric equations: do I need to consider different cases in this example?
I'm trying to solve this set of trigonometric equations:
tan ( δ + β 2 ) = c tan ( θ 2 ) b tan ( δ β 2 ) = a cos ( δ + β 2 ) cos ( γ 2 ) = cos ( θ 2 )
Where a,b,c and θ are some given (but random) real numbers (they could be 0 and π). The goal is to solve for the real values of γ , β and δ. I'm trying to solve these equations by combining some variables. Let
M = δ + β 2 , N = δ β 2 , P = γ 2
then it's easy to solve for M from equation 1. However, to solve for δ and β, we also need to figure out N. I'm worried that if I need to discuss the solutions by cases, like if θ = π (so that tan θ 2 is undefined) or if a or b is equal to 0. Any suggestions on solving for this question? Is it possible to obtain a generalized solution? Thanks!!

Answer & Explanation

Kristen Garza

Kristen Garza

Beginner2022-11-19Added 13 answers

Look at:
M + N = δ
M N = β
You can find M , N from your first two equations, and then calculate δ , β from those.
For γ, note that
tan 2 ( α ) + 1 = 1 cos 2 α
From this, you can write
cos α = ± 1 tan 2 α + 1
(depending on the angle).
Then this:
cos ( δ + β 2 ) cos ( γ 2 ) = cos ( θ 2 )
Becomes this:
cos ( γ 2 ) = cos ( θ 2 ) tan 2 ( δ + β 2 ) + 1

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