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Solving a linear equation involving the sine function

Find all possible exact solutions for the equation sin t = 1 2 .

Solving for all possible values of t means that solutions include angles beyond the period of 2 π . From [link] , we can see that the solutions are π 6 and 5 π 6 . But the problem is asking for all possible values that solve the equation. Therefore, the answer is

π 6 ± 2 π k   and   5 π 6 ± 2 π k

where k is an integer.

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Given a trigonometric equation, solve using algebra .

  1. Look for a pattern that suggests an algebraic property, such as the difference of squares or a factoring opportunity.
  2. Substitute the trigonometric expression with a single variable, such as x or u .
  3. Solve the equation the same way an algebraic equation would be solved.
  4. Substitute the trigonometric expression back in for the variable in the resulting expressions.
  5. Solve for the angle.

Solve the trigonometric equation in linear form

Solve the equation exactly: 2 cos θ 3 = 5 , 0 θ < 2 π .

Use algebraic techniques to solve the equation.

2 cos θ 3 = 5         2 cos θ = 2           cos θ = 1                θ = π
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Solve exactly the following linear equation on the interval [ 0 , 2 π ) : 2 sin x + 1 = 0.

x = 7 π 6 , 11 π 6

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Solving equations involving a single trigonometric function

When we are given equations that involve only one of the six trigonometric functions, their solutions involve using algebraic techniques and the unit circle (see [link] ). We need to make several considerations when the equation involves trigonometric functions other than sine and cosine. Problems involving the reciprocals of the primary trigonometric functions need to be viewed from an algebraic perspective. In other words, we will write the reciprocal function, and solve for the angles using the function. Also, an equation involving the tangent function is slightly different from one containing a sine or cosine function. First, as we know, the period of tangent is π , not 2 π . Further, the domain of tangent is all real numbers with the exception of odd integer multiples of π 2 , unless, of course, a problem places its own restrictions on the domain.

Solving a problem involving a single trigonometric function

Solve the problem exactly: 2 sin 2 θ 1 = 0 , 0 θ < 2 π .

As this problem is not easily factored, we will solve using the square root property. First, we use algebra to isolate sin θ . Then we will find the angles.

2 sin 2 θ 1 = 0        2 sin 2 θ = 1          sin 2 θ = 1 2        sin 2 θ = ± 1 2            sin θ = ± 1 2 = ± 2 2                 θ = π 4 , 3 π 4 , 5 π 4 , 7 π 4
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Solving a trigonometric equation involving cosecant

Solve the following equation exactly: csc θ = 2 , 0 θ < 4 π .

We want all values of θ for which csc θ = 2 over the interval 0 θ < 4 π .

csc θ = 2 1 sin θ = 2 sin θ = 1 2       θ = 7 π 6 , 11 π 6 , 19 π 6 , 23 π 6
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Solving an equation involving tangent

Solve the equation exactly: tan ( θ π 2 ) = 1 , 0 θ < 2 π .

Recall that the tangent function has a period of π . On the interval [ 0 , π ) , and at the angle of π 4 , the tangent has a value of 1. However, the angle we want is ( θ π 2 ) . Thus, if tan ( π 4 ) = 1 , then

θ π 2 = π 4 θ = 3 π 4 ± k π

Over the interval [ 0 , 2 π ) , we have two solutions:

3 π 4   and  3 π 4 + π = 7 π 4
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Questions & Answers

for the "hiking" mix, there are 1,000 pieces in the mix, containing 390.8 g of fat, and 165 g of protein. if there is the same amount of almonds as cashews, how many of each item is in the trail mix?
ADNAN Reply
linear speed of an object
Melissa Reply
an object is traveling around a circle with a radius of 13 meters .if in 20 seconds a central angle of 1/7 Radian is swept out what are the linear and angular speed of the object
Melissa
test
Matrix
how to find domain
Mohamed Reply
like this: (2)/(2-x) the aim is to see what will not be compatible with this rational expression. If x= 0 then the fraction is undefined since we cannot divide by zero. Therefore, the domain consist of all real numbers except 2.
Dan
define the term of domain
Moha
if a>0 then the graph is concave
Angel Reply
if a<0 then the graph is concave blank
Angel
what's a domain
Kamogelo Reply
The set of all values you can use as input into a function su h that the output each time will be defined, meaningful and real.
Spiro
how fast can i understand functions without much difficulty
Joe Reply
what is inequalities
Nathaniel
functions can be understood without a lot of difficulty. Observe the following: f(2) 2x - x 2(2)-2= 2 now observe this: (2,f(2)) ( 2, -2) 2(-x)+2 = -2 -4+2=-2
Dan
what is set?
Kelvin Reply
a colony of bacteria is growing exponentially doubling in size every 100 minutes. how much minutes will it take for the colony of bacteria to triple in size
Divya Reply
I got 300 minutes. is it right?
Patience
no. should be about 150 minutes.
Jason
It should be 158.5 minutes.
Mr
ok, thanks
Patience
100•3=300 300=50•2^x 6=2^x x=log_2(6) =2.5849625 so, 300=50•2^2.5849625 and, so, the # of bacteria will double every (100•2.5849625) = 258.49625 minutes
Thomas
158.5 This number can be developed by using algebra and logarithms. Begin by moving log(2) to the right hand side of the equation like this: t/100 log(2)= log(3) step 1: divide each side by log(2) t/100=1.58496250072 step 2: multiply each side by 100 to isolate t. t=158.49
Dan
what is the importance knowing the graph of circular functions?
Arabella Reply
can get some help basic precalculus
ismail Reply
What do you need help with?
Andrew
how to convert general to standard form with not perfect trinomial
Camalia Reply
can get some help inverse function
ismail
Rectangle coordinate
Asma Reply
how to find for x
Jhon Reply
it depends on the equation
Robert
yeah, it does. why do we attempt to gain all of them one side or the other?
Melissa
how to find x: 12x = 144 notice how 12 is being multiplied by x. Therefore division is needed to isolate x and whatever we do to one side of the equation we must do to the other. That develops this: x= 144/12 divide 144 by 12 to get x. addition: 12+x= 14 subtract 12 by each side. x =2
Dan
whats a domain
mike Reply
The domain of a function is the set of all input on which the function is defined. For example all real numbers are the Domain of any Polynomial function.
Spiro
Spiro; thanks for putting it out there like that, 😁
Melissa
foci (–7,–17) and (–7,17), the absolute value of the differenceof the distances of any point from the foci is 24.
Churlene Reply

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Source:  OpenStax, Precalculus. OpenStax CNX. Jan 19, 2016 Download for free at https://legacy.cnx.org/content/col11667/1.6
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