Practicing Success

Target Exam

CUET

Subject

General Test

Chapter

Quantitative Reasoning

Topic

Trigonometry

Question:

If $cos(A - B) =\frac{\sqrt{3}}{2}$, and $cos(A + B) = 0$, where A and B are positive acute angles and A ≥ B, then the measures of A and B are:

Options:

80° and 10°

60° and 30°

70° and 20°

50° and 40°

Correct Answer:

60° and 30°

Explanation:

We are given that ,

cos ( A - B ) = \(\frac{ √3 }{2}\)

& cos ( A + B ) = 0

{ we know , cos 30º = \(\frac{ √3 }{2}\)  & cos 90º = 0 }

So ,

A - B = 30º  ----(1)

A + B = 90º   ---(2)

On adding  1 and 2.

2A = 120º

A = 60º

Now,

60º - B = 30º

B = 30º

Ans :-  60º and 30º