RRB NTPC Mains or Stage 2 Model Paper 5 with solutions

© examsiri.com

Question : 20 of 120

Marks: +1, -0

What is the expression :

(sin^4 x – cos^4 x + 1) cosec^2

x equal to?

1
2
0
–1

Solution:

(b) (

sin^4 x – cos^4

x + 1)

cosec^2

x= {(

sin^2 x – cos^2 x

) (

sin^2 x + cos^2 x

) + 1}

cosec^2 x

[(∴ a^2 – b^2 = (a + b) (a – b)]

= (

sin^2 x – cos^2 x + 1

)

cosec^2 x

=

(sin^2 x + sin^2 x) cosec^2 x

(∴ 1 – cos^2 x = sin^2 x)

=

2 sin^2 x .

1/{sin^2 x}= 2

© examsiri.com

Go to Question:

Prev Question

Next Question