Question

In the following figure  the value of cos ϕ is 

विकल्प

• \[\frac{5}{4}\]

• \[\frac{5}{3}\]

• \[\frac{3}{5}\]

• \[\frac{4}{5}\]

Answer 1

We should proceed with the fact that sum of angles on one side of a straight line is180°.

So from the given figure, 

θ+∅+90°=180° `

So , `θ=90°-∅.............(1) ` 

Now from the triangle ΔABC, 

`sin ∅=4/5` 

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

`sin(90°-∅)=4/5` 

Therefore, `cos∅=4/5`