In triangle ABC, angle C is 90, sin A = √7 / 4. Find cos A

Given: right-angled triangle ABC;
angle C = 90;
sin A = √7 / 4;
Find: cos A -?
Solution:
Consider a right-angled triangle ABC.
Let’s use the basic trigonometric formula:
cos ^ 2A + sin ^ 2A = 1;
cos ^ 2A = 1 – sin ^ 2A;
cos ^ 2A = 1 – (√7 / 4) ^ 2;
cos ^ 2A = 1 – 7/16 (represent one integer as a mixed fraction with denominator 16);
cos ^ 2A = 16/16 – 7/16;
cos ^ 2A = 9/16;
cos A = √ (9/16);
cos A = 3/4.
Answer: cos A = 3/4.