Question

Which of the following value is not a possible value of Cos x​

Answer 1

Answer:

cos x = -1

Step-by-step explanation:

cotx+cosecx=5

sinx

cosx

+

sinx

1

=5

cosx+1=5sinx

squaring both sides

(cosx+1)

2

=(5sinx)

2

cos

2

x+1+2cosx=25sin

2

x

cos

2

x+1+2cosx=25(1−cos

2

x)

26cos

2

x+2cosx−24=0

dividing by 2 we get

13cos

2

x+13cosx−12cosx−12=0

13cosx(cosx+1)−12(cosx+1)=0

(13cosx−12)(cosx+1)

cosx=

13

12

or

cosx=−1