cos ( x - y ) / cos x cos y = 1 + tan x tan y is proven as explained below.
<h3>Further explanation</h3>
Firstly , let us learn about trigonometry in mathematics.
Suppose the ΔABC is a right triangle and ∠A is 90°.
<h3>sin ∠A = opposite / hypotenuse</h3><h3>cos ∠A = adjacent / hypotenuse</h3><h3>tan ∠A = opposite / adjacent </h3>
There are several trigonometric identities that need to be recalled, i.e.




Let us now tackle the problem!
In this problem , we will use identity as follows:

Given:





<h3>Learn more</h3>
<h3>Answer details</h3>
Grade: College
Subject: Mathematics
Chapter: Trigonometry
Keywords: Sine , Cosine , Tangent , Opposite , Adjacent , Hypotenuse , Triangle , Fraction , Lowest , Function , Angle