Question

In Fig. 5.47, the value of cos ϕ is



(a) $\frac{5}{4}$
(b) $\frac{5}{3}$
(c) $\frac{3}{5}$
(d) $\frac{4}{5}$

Answer 1

We should proceed with the fact that sum of angles on one side of a straight line is.

So from the given figure,

So, …… (1)

Now from the triangle,

Now we will use equation (1) in the above,

Therefore,

So the answer is