SOLUTION: Tangent (theta) + square root of 3 = secant (theta) I tried squaring both sides but in the end I never result with the correct answer. I'm not sure how to start this one or wh

Algebra ->  Trigonometry-basics -> SOLUTION: Tangent (theta) + square root of 3 = secant (theta) I tried squaring both sides but in the end I never result with the correct answer. I'm not sure how to start this one or wh      Log On


   



Question 1049302: Tangent (theta) + square root of 3 = secant (theta)

I tried squaring both sides but in the end I never result with the correct answer. I'm not sure how to start this one or what I am doing wrong.

Answer by ikleyn(52803) About Me  (Show Source):
You can put this solution on YOUR website!
.
Tangent (theta) + square root of 3 = secant (theta)

I tried squaring both sides but in the end I never result with the correct answer.
I'm not sure how to start this one or what I am doing wrong.
~~~~~~~~~~~~~~~~~~~~~~

So, you are trying to solve an equation

tan(x) + sqrt%283%29 = sec(x).

It is the same as

sin%28x%29%2Fcos%28x%29 + sqrt%283%29 = 1%2Fcos%28x%29.

Multiply both sides by cos(x). You will get

sin%28x%29 + sqrt%283%29%2Acos%28x%29 = 1.


Multiply both sides by 1%2F2. You will get

%281%2F2%29%2Asin%28x%29 + %28sqrt%283%29%2F2%29%2Acos%28x%29 = 1%2F2.


Recall that 1%2F2 = cos%28pi%2F3%29,  sqrt%283%29%2F2 = sin%28pi%2F3%29.

Therefore, you can write the last equation as 

cos%28pi%2F3%29%2Asin%28x%29+%2B+sin%28pi%2F3%29%2Acos%28x%29 = 1%2F2.


Apply the addition formula for sine.  ( It is cos(a)*sin(b) + sin(a)*cos(b) = sin(a+b). 
                                        See the lesson Addition and subtraction formulas in this site ). You will get

sin%28x+%2B+pi%2F3%29 = 1%2F2.

It implies  x+%2B+pi%2F3 = pi%2F6  or  x+%2B+pi%2F3 = 5pi%2F6.

Hence,  x = pi%2F6-pi%2F3 = -pi%2F6  or  x = 5pi%2F6-pi%2F3 = 3pi%2F6 = pi%2F2.

The last root doesn't fit due to "sec" in the original equation.


Answer.  x = -pi%2F6,  or  -pi%2F6+%2B+2k%2Api for any integer "k".

See also the lessons
    - Solving simple problems on trigonometric equations
    - Solving more complicated problems on trigonometric equations
    - Solving advanced problems on trigonometric equations
in this site.