Share

## In triangle ABC, angle C is right angle. AB =29, BC =21 then value cos²B + sin²B.

Question

In triangle ABC, angle C is right angle. AB =29, BC =21 then value cos²B + sin²B.

in progress
0

Mathematics
1 month
2021-08-16T07:16:59+00:00
2021-08-16T07:16:59+00:00 1 Answers
0 views
0
## Answers ( )

Answers:

By Pythagoras theorem,

AB

2

=AC

2

+BC

2

⇒AC

2

=AB

2

−BC

2

⇒AC

2

=29

2

−21

2

=(29+21)(29−21)=50×8

⇒AC

2

=25×16

⇒AC=5×4=20 units

⇒cosθ=

AB

BC

=

29

21

,

sinθ=

AB

AC

=

29

20

⇒sin2θ+cos

2

θ=

29

2

21

2

+20

2

=

29

2

29

2

=1

⇒cos

2

θ−sin

2

θ=

29

2

21

2

−20

2

=

841

41

.