So, cos x = 0 implies x = (2n + 1)π/2 , where n takes the value of any integer. For a triangle, ABC having the sides a, b, and c opposite the angles A, B, and C, the cosine law is defined. In the same way, we can derive other values of cos degrees like 30°, 45°, 60°, 90°, 180°, 270°and 360

Step-by-step explanation:

if sin a= 3/4 then a = 50

if sin = 4/5 then a = 60

if sin = 2/3 then a = 40

But we can perfect this

if sin = 4/5 then a = 57 as 4/5 = 0.83

We want 0.8 = 4/5

if sin = 4/5 then a = 54 as 4/5 = 0.809

if sin = 4/5 then a = 53.5 as 4/5 = 0.80385

Now for cos

It is much easier than it initially appears. Remember the definition of SINE:

SINΘ = opp In your case, that means the opposite is 4/5 = 0.80385 (yes, ignore the sign for now) and the hypotenuse is 11.48910018

hyp Please draw that triangle right now, because it will help you a lot at the end.

53.50 degree Remember to place the angle in the appropriate spot.

Now, use the Pythagorean Theorem to find the missing side (easy, right? It's 9.534) and place it in the adjacent position.

You can easily find all of the trig functions now!

Simply remember that:

COSΘ = Adj with SEC the reciprocal of this one

Hyp

TANΘ = Opp COT the reciprocal of TAN and, if anyone asks, CSC coming from SIN.

Adj

I told you to ignore the signs, but now we can't anymore. Remember the four quadrants and the memory trick:

A -- ALL are positive

Smart -- SIN and CSC are positive

Trig -- TAN & COT are positive

Class -- COS and SEC are positive.

Since your SIN was negative, it must be in III or 6, and COS is positive in I and 6 So we're in quadrant 6 then!

Only your COS and SEC will be positive, the rest negative

7 0

3 years ago