Trigonometric functions which are related by having the same value at complementary angles are called cofunctions. Cofunctions of complementary angles are equal.
A. csc 20' = csc(90-70)=sec 70
B. cos 87' =  cos (90-3)=sin 3' 
C. csc 40' =  csc(90-50) =sec50'  
D. tan 15' = tan(90-75)= cot 75'
Among all the option  c is not correct.
Option C is false.
 
        
                    
             
        
        
        
To solve, set an equation:
First Number: x
Second Number: 2x
x+2x=36
3x=36
divide both sides by 3
x=13
First Number: (x) 12
Second Number: (2x) 24
Answers: 12 and 24
        
                    
             
        
        
        
Answer:
2/3 , 13/18, 7/9 , 5/6 (least to greatest order)
Step-by-step explanation:
1.  You need to convert all the fractions into decimal form . 
2. 7/9.00 = 0.78 (rounded)
3. 13/18.00 = 0.72
4. 5/6.00 = 0.83
5 . 2/3.00= 0.67 (rounded)
 
        
             
        
        
        
Let us assume last year the price of the item = $x.
After increase in price by 15% the new price = x + 15% of x = x+ 0.15x = 1.15x.
There is a 25% discount for employee.
25% of 1.15x = 0.25 × 1.15x = 0.2875 x.
Price after discount = 1.15x - 0.2875 x = 0.8625x.
The employee pays $172.50.
Therefore, 
0.8625x = 172.50.
Dividing both sides by 0.08625.

<h3>x=200.</h3><h3>Therefore, last year the price was $200.</h3>
 
        
             
        
        
        
This is completing the square:
(x^2+12x+36)+42-36
Answer: (x+6)^2 +6