# Casio fx-991es plus

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#1
Hi,

Basically I am doing C3 and currently doing differentiating using chain rule, product rule etc. I always check my answer using the CAsio fx-991es plus by like substituting a value for x and see if it is the same. Everything seems to work, ln(x), e^x but for some reason it does not work for differentiating trigonometric functions? Is it possible? Also, is there a way to check your answer with you calculator for differentiating implicitly?

Cheers
0
5 years ago
#2
(Original post by ssargithan)
Hi,

Basically I am doing C3 and currently doing differentiating using chain rule, product rule etc. I always check my answer using the CAsio fx-991es plus by like substituting a value for x and see if it is the same. Everything seems to work, ln(x), e^x but for some reason it does not work for differentiating trigonometric functions? Is it possible? Also, is there a way to check your answer with you calculator for differentiating implicitly?

Cheers
Are you remembering to be in radian mode?
0
#3
(Original post by tiny hobbit)
Are you remembering to be in radian mode?
Works now THANKS thought it would work in degree mode as well :/
0
5 years ago
#4
(Original post by ssargithan)
Works now THANKS thought it would work in degree mode as well :/
1
5 years ago
#5
(Original post by ssargithan)
Works now THANKS thought it would work in degree mode as well :/
Differentiating sin x only gives cos x if x is in radians (that's why you were introduced to them in C2. If x is in degrees, differentiating sin x gives (pi/180) cos x
1
5 years ago
#6
(Original post by Chlorophile)
Do you mean calculus? Both radians and degrees are used in C3 trig.

@ssargithan Always use radians when doing calculus involving trig functions. If you were to use degrees then certain things you've learnt won't apply anymore e.g.

assumes that x is measured in radians.

But in degrees:

1
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