Guidelines
Simple Identities
First Step
Is It An Identity?
Substitutions
100

Complete this statement: Two functions  f(x) and  g(x) are identically equal if  f(x) = g(x) for any real number  x \in mathbb R for ...

What is "which both functions are defined"? 

100

This ratio in terms of sines and cosines is the same as  tan(theta) 

What is 

sin(theta)/cos(theta)?

100

The first step to establish the identity: 

cot(x)/csc(x) = cos(x)

What is rewrite left side in terms of sines and cosines? 

100

 csc(x) cdot cos(x) = tan(x) 

What is no?

100

The trigonometric substitution for  x that makes  x/sqrt(1-x^2) equal to  tan(x) for  0 < theta < pi/2 

What is 

x=sin(theta)?

200

True or False: When proving identities, it is common to change any trigonometric function to its sine or cosine equivalent. 

What is True?

200

The reciprocal of cosine. 

What is secant?

200

The first step in establishing the identity 

csc(x) cdot tan(x) = sec(x)

What is rewrite the left side in terms of sines and cosines?

200

 sec(x) \cdot sin(x) = tan(x) 

What is yes?

200

The trigonometric substitution  x=tan(theta) for  0 < theta < pi/2 makes  sqrt(1+x^2) simplify to this.

What is 

sec(x)?

300

Complete the statement: It is common to begin proving an identity with the side that is ...

What is "more complicated"?

300

The two trigonometric functions that are even functions. 

What are cosine and secant? 

300

The first step in establishing the identity 

sin^2(-x) + cos^2(-x) = 1

What is use the even-odd properties? 

300

 cos(x)(tan(x) + cot(x)) = csc(x) 

What is yes?

300

The trigonometric substitution that makes  sqrt(x^2 - 1)  simplify to  tan(theta) for  0 < theta < pi/2 .

What is 

x=sec(theta)?

400
True or False: When establishing an identity, it is permitted to add a quantity to both sides of the equation to help in establishing the validity of the statement. 

What is False? 

400

If we know  sin^2(theta) + cos^2(theta) = 1 , obtain  tan^2(theta) + 1 = sec^2(theta) by doing this. 

What is divide both sides by the square of the cosine? 

400

The first step in establishing the identity 

sin(x)/(1+cos(x)) + (1+cos(x))/sin(x) = 2csc(x)

What is add the fractions on the left side? 

400

 tan(u)cot(u) - cos^2(u) = sin(u) 

What is no? 

400

If we have  sqrt(9-x^2) and we substitute  x = 3sin(theta) for  0 < theta < pi/2 , the expression simplifies to this. 

What is 

3cos(theta)?

500

True or False: Cross Multiplying is permitted when proving trigonometric identities

What is False?

500

 ln|sec(x) + tan(x)| + ln|sec(x) - tan(x)| =  

What is zero? 

500

The first step in establishing the identity 

(1-sin(x))/cos(x) = cos(x)/(1+sin(x))

What is multiply the numerator and denominator on the left side by 

1+sin(x)?

500

 3sin^2(x) + 4cos^2(x) = 3 - cos^2(x) 

What is no? 

500

If we have  sqrt(x^2 - 25)/x and we make the trigonometric substitution  x = 5 sec(theta) for  0 < theta < pi/2 , the expression simplifies to this. 

What is 

cos(theta)?

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