Question

Which of the following options represents a logical first step that can be used

to prove the trigonometric identity
cos(x)/ cos(x)+sin(x)tan(x)=cos^2(x)?

Answer 1

Answer: Option B.

Explanation:

Here we can start with the relation

cos(x)^2 + sin(x)^2 = 1

multiply both sides by cos(x)

cos(x) = cos(x)^3 + sin(x)^2*cos(x) = cos(x)^2*(cos(xI + sin(x)^2/cos(x))

now we can replace sin(x)/cos(x) = tg(x)

cos(x) = cos(x)^2*(cos(x) + sin(x)*tan(x))

So the correct option is B