Question

In a right triangle ABC, angle C is a right angle and cos B =255/257.

What is the measure or angle A?

A)7.2 degrees

B)83.2 degrees

C)82.8 degrees

D)90.0 degrees

Answer 1

C

Explanation:

Given

cosB =
`(adjacent)/(hypotenuse)` =
`(BC)/(A B)` =
`(255)/(257)`

Then the hypotenuse AB = 257 and BC = 255

sinA =
`(opposite)/(hypotenuse)` =
`(BC)/(AB)` =
`(255)/(257)`

A =
`sin^(-1)` (
`(255)/(257)`) = 82.8° → C