Question

I need the answer of Q31
Please help

Answer 1

Answer:

hlo dear

Step-by-step explanation:

given side = 4 cm

two cubes are joined

therefore the area of resulting cuboid is

length of cube = 2×4 =8 cm

breadth = a = 4 cm

t.s. a = 2 ( lb + bh + hl )

2( 8× 4 + 4×4 + 8 × 4)

2 ( 32 + 16 + 32)

2(80) = 160

answer is 160 cm sq .

hope this helps u

Answer 2

Step-by-step explanation:

we know that:

>> Cos 30° = √3 / 2

>> Sin 30° = 1 / 2

>> Cos 90° = 0

>> Sin 90° = 1

Given that

>> @ = 30°

so, 3@ will be 90°

We have to show that ;

(1) Cos 3@ = 4Cos³@ - 3 Cos@

and

(2) Sin 3@ = 3Sin@ - 4 Sin³@

Now, Taking (1) ...

Cos 3@ = 4Cos³@ - 3 Cos@

=> Putting value of @

=> Cos 90° = 4Cos³30° - 3 Cos30°

=> 0 = 4 × (√3 / 2 )³ - 3 × (√3 / 2)

=> 0 = 4 × (3√3 / 8) - 3√3 / 2

=> 0 = 3√3 / 2 - 3√3 / 2

=> 0 = 0

Now, Taking (2) ...

Sin 3@ = 3Sin@ - 4 Sin³@

=> Putting value of @

=> Sin 90° = 3Sin30° - 4 Sin³30°

=> 1 = 3 × (1/2) - 4 × (1/2)³

=> 1 = (3 / 2) - (4 / 8)

=> 1 = (3 / 2) - (1 / 2 )

=> 1 = 1

Hence, Verified...

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