Question

if cos theta =-3/5
and 180° <theta< 270° then cosec theta is​

Answer 1

Answer:

180

∘

θ<270

∘

⇒90

∘

<

2

θ

<135

∘

cos

2

θ=1−sin

2

θ=1−

25

9

=

25

16

180

∘

<θ<270

∘

cos

2

θ=

25

16

⇒cosθ=−

5

4

cos

2

2

θ

=

2

1+cosθ

=

2

1−4/5

=

10

1

90

∘

<θ/2<135

∘

cos

2

(θ/2)=

10

1

⇒cos(θ/2)=−

10

1