In ∆ABC, cosC + cosAc + a&nbs

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 Multiple Choice QuestionsMultiple Choice Questions

171.

tanθ + cotθ = 2 = 2, then sinθ is equal to

  • 12

  • 13

  • 12

  • 1


172.

If θ = π6, then the 10th term of  1 + cosθ + isinθ + cosθ + isinθ2 + cosθ + isinθ3 + ...is equal to

  • i

  • - 1

  • 1

  • - i


173.

sin5θsinθ is equal to 

  • 16cos4θ - 12cos2θ + 1

  • 16cos4θ+ 12cos2θ + 1

  • 16cos4θ - 12cos2θ - 1

  • 16cos4θ + 12cos2θ - 1


174.

cos2π6 + θ - sin2π6 + θ is equal to

  • 12cos2θ

  • 0

  • - 12cos2θ

  • 12


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175.

In ABC, cosC + cosAc + a + cosBb is equal to

  • 1a

  • 1b

  • c + ab

  • 1


B.

1b

We have,cosC +cosAc +a  = cosC +cosA2R(sinC +sinA)                            = 2cosC + A2cosC - A22R . 2sinC + A2cosC - A2 = 12RtanB2Also,           cosBB = cosB2RsinB = 12R 1 - tanB2 2tanB2  cosC + cosAc + a + cosBb = 12Rtan B2 + 12R 1 -tanB22tanB2                                                      =12R2tan2B2 + 1 -tan2B22tanB2                                                      = 12R1 + tanB2 2tanB2                                                      = 12RsinB = 1b


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176.

In ABC, ab2 - c2 + cb2 - a2 = 0, then B is equal to 

  • π2

  • π4

  • 2π3

  • π3


177.

In ABC,a2sin(2C) + c2sin(2A) is equal to 

  • 2

  • 3

  • 4


178.

The shadow of a tower standing on a level ground is found to be 60m longer when the sun'saltitude is 30° than when it is 45°.The height of the tower is 

  • 30m

  • 90m

  • 603m

  • 303 + 1m


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179.

If cosecθ = p + qp - q,then cotπ4 + θ4 is equal to

  • pq

  • qp

  • pq

  • pq


180.

From a point on the level ground, the angle of elevation of top of a pole is 30° on moving 20metres nearer,the angle of elevation is 45°. Then,the height of the pole in metres, is

  • 103 - 1

  • 103 - 1

  • 15

  • 20


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