Q34 of 143 Page 6

In Fig. 5.47, the value of cos ϕ is

As we know that sum of the angles of the straight line is 180°,


Therefore,


∠ θ + ∠90 + ∠ϕ = 180


∠ θ + ∠ϕ = 90


In ∆ABC,


sin θ = 4/5 = p/h


Putting θ = 90 - ϕ


We get,


sin (90 - ϕ) = 4/5


As,


Sin (90 - ϕ) = cos ϕ


cos ϕ = 4/5

More from this chapter

All 143 →
31

If cos θ = 2/3 then 2 sec2θ + 2tan2θ – 4 is equal to

 32

tan 5° × tan 30° × 4 tan 85° is equal to

 33

The value of + cot1° cot 2° cot 3°.... cot 90°, is

 35

In Fig. 5.48, AD = 4 cm BD = 3 cm and CB = 12 cm, find cot θ.