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Monday, June 10, 2013

Coterminal Angles

Category: Trigonometry

"Published in Suisun City, California, USA"

Find an angle between 0° and 360° that is coterminal with the given angle:

a. 2223°
b. -400°
c. 1270°
d. -800°

Solution:

Coterminal angles are angles in standard position (angles with the initial side on the positive x-axis) that have a common terminal side (angles less than 360°). Usually, coterminal angles are more than 360°. To simplify a coterminal angle, divide a given angle by 360° which is equivalent to 1 revolution. The remainder or a fraction of a revolution will be the terminal side. Let's have the examples of the following:

a. 2223°

    Since the given angle is positive, then it is rotated counterclockwise from positive x-axis (initial side) to terminal side.


After six complete revolution from positive x-axis in a counterclockwise direction, there's an excess angle of 



which is located at the first quadrant.

Photo by Math Principles in Everyday Life

b. - 400°

    Since the given angle is negative, then it is rotated clockwise from positive x-axis (initial side) to terminal side.


After one complete revolution from positive x-axis in a clockwise direction, there's an excess angle of


which is located at the fourth quadrant.

Photo by Math Principles in Everyday Life

c. 1270°

    Since the given angle is positive, then it is rotated counterclockwise from positive x-axis (initial side) to terminal side.


After three complete revolution from positive x-axis in a counterclockwise direction, there's an excess angle of 



which is located at the third quadrant.

Photo by Math Principles in Everyday Life

 d. - 800°

 Since the given angle is negative, then it is rotated clockwise from positive x-axis (initial side) to terminal side.


After two complete revolution from positive x-axis in a clockwise direction, there's an excess angle of


 which is located at the fourth quadrant.

 
Photo by Math Principles in Everyday Life

Sunday, June 9, 2013

Solving Exponential Equations, 2

Category: Algebra

"Published in Suisun City, California, USA"

Find the value of x for


Solution:

Consider the given equation above



This type of exponential equation is considered a difficult one because their bases are different. You need to take natural logarithm on both sides of the equation in order to solve for the value of x in their exponents. Take natural logarithm on both sides of the equation, we have















Or, if you will use a calculator, x will be equal to


  





Saturday, June 8, 2013

Solving Trigonometric Equations, 5

Category: Trigonometry

"Published in Suisun City, California, USA"

Solve for the value of x for


Solution:

Consider the given equation above


As you notice that all trigonometric functions have different angles. In this type of trigonometric equation, we have to use the Sum to Product Formulas. The left side of the equation can be written as












Note: I am strongly advice to memorize or remember all trigonometric identities and formulas as much as you can because you will use those in proving the trigonometric identities and even in higher Math subjects like Differential Calculus, Integral Calculus, and Differential Equations.