To solve the inequality cos(x−6π)≥−21, let's follow these steps:
Step 1: Solve the related equation
Start by solving the equation cos(x−6π)=−21.
We know that cos(θ)=−21 at specific angles, namely:
θ=32π+2nπorθ=34π+2nπ
for any integer n.
Thus, for the equation cos(x−6π)=−21, we have:
x−6π=32π+2nπorx−6π=34π+2nπ
Step 2: Solve for x
Now solve these two equations for x:
-
x−6π=32π+2nπ
x=32π+6π+2nπ=64π+6π+2nπ=65π+2nπ
-
x−6π=34π+2nπ
x=34π+6π+2nπ=68π+6π+2nπ=69π+2nπ=23π+2nπ
Thus, the solutions to the equation cos(x−6π)=−21 are:
x=65π+2nπorx=23π+2nπ
Step 3: Analyze the inequality
The inequality cos(x−6π)≥−21 means x−6π must be within the range of angles where cos(θ) is greater than or equal to −21.
For cos(θ)≥−21, the angles θ are within the range:
−3π≤θ≤35π
This corresponds to the interval for x−6π. So, we must solve:
−3π≤x−6π≤35π
Step 4: Adjust for x
Add 6π to each part of the inequality:
−3π+6π≤x≤35π+6π
Simplifying:
−62π+6π=−6π,35π+6π=610π+6π=611π
Thus, the inequality becomes:
−6π≤x≤611π
Step 5: General Solution
The general solution is the set of all x values such that:
−6π≤x≤611π+2nπ
where n is any integer, since the cosine function has a period of 2π.
Final Answer:
The solution to the inequality cos(x−6π)≥−21 is:
x∈[−6π,611π]+2nπ,n∈Z
Would you like any additional details or clarifications?
Related Questions:
- How would the solution change if the inequality was cos(x−6π)≤−21?
- How can you graph the function y=cos(x−6π) to visualize this inequality?
- What other trigonometric inequalities are commonly solved in similar ways?
- How can you apply this solution to real-world problems?
- How does shifting the cosine function affect the solution to the inequality?
Tip:
When solving trigonometric inequalities, always consider the periodic nature of the functions and adjust the range of solutions accordingly by adding multiples of the period.