Question

 In ΔABC ,∠B= 90° ∠C=60°. ∠A =300  AC= 20 cm .find  BC​

Answer 1

∠A+∠B+∠C=180

∘

⇒30

∘

+∠B+90

∘

=180

∘

[∵∠A=30

∘

and∠C=90

∘

]

⇒∠B=180

∘

−120

∘

=60

∘

Now , cosA=

AB

AC

⇒cos30

∘

=

40

AC

⇒

2

3

=

40

AC

⇒AC=

2

3

×40⇒AC=20

3

units

and , sinA=

AB

BC

⇒sin30

∘

=

40

BC

⇒

2

1

=

40

BC

⇒=40×

2

1

=20 units

Hence AC = 20

3

units , BC=20 units and ∠B=60

∘

Answer 2

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