Question

Angle 0 lies in the second quadrant, and sin 0=3/5 Cos 0=

Answer 1

Answer:

-4/5

Step-by-step explanation:

Please use a symbol such as x or Ф to represent an angle; your 0 is too easily confused with zero.

If Angle Ф lies in the second quadrant, and sin Ф=3/5, find cos Ф.

The sine of an angle is the ratio of the length of the opposite side to the length of the hypotenuse:  sin Ф = opp / hyp = 3 / 5.  Thus the opp side has length 3 and the hyp has length 5.  By the Pythagorean Theorem,

the adj side has length √(5² - 3²), or √(25-9), or √16, or ±4.  Because the angle is in the 2nd quadrant, choose adj = -4.

Then the cosine of this angle is  cos Ф = adj / hyp = -4 / 5