If cos (x + 25)o = sin 45o, find the value of x

Assessment: WAEC SSCE - General Mathematics - 2008 (Objective) Subject: General Mathematics

Question 1 Report

If cos (x + 25)o = sin 45o, find the value of x
Answer Details
We know that cos (90o - A) = sin A. So, cos (x + 25o) = cos (90o - 45o) = cos 45o. Since cos A = cos B implies A = ±B + 360on, we have: x + 25o = ±45o + 360on x = -25o ± 45o + 360on x = 20o + 360on or x = 70o + 360on Since we are given the range of x, we take x = 20o. Therefore, the value of x is 20o.

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