Question

.in triangle abc, right angled at b. if tan a=1/root 3, find the value of cos a cos c+ sin a sin c​

Answer 1

ANSWER

In △ABC,

∠B=90

o

, tanA=

3

1

=

AB

BC

Let BC =1x,AB=

3

x

AC

2

=AB

2

+BC

2

AC

2

=(

3

x)

2

+(x)

2

=4x

2

AC=2x

(i) sinAcosC+cosAsinC=

2

1

×

2

1

+

2

3

×

2

3

=

4

1

+

4

3

=1

(ii) cosAcosC−sinAsinC=

2

3

×

2

1

−

2

1

×

2

3

=

4

3

−

4

3

=0