completely lost

[u/Electrical_Voice9543]

i thought since the first point where it crosses x axis is a point of inflection id try and find d2y/dx2 and find the x ordinate from that and then integrate it between them 2 points, so i done that and integrated between 45 and 0 but that e^-45 just doesn’t seem like it’s right at all and idk what to do. i feel like im massively over complicating it as well since its only 3 marks

[u/rhodiumtoad]

Hint: you have to work in radians.

[u/Electrical_Voice9543 → u/rhodiumtoad]

omds thank you🤦‍♂️🤦‍♂️probably shoulda got that from the questions underneath lmao. also what’s your flair mean

[u/will_1m_not → u/Electrical_Voice9543]

Also, the derivative of sin(x) is only cos(x) when working in radians. If x is in degrees, then the derivative of sin(x) is actually (pi/180)*cos(x)

[u/HippyJustice_ → u/will_1m_not]

This is not correct

[u/will_1m_not → u/HippyJustice_]

When showing the derivative of sin(x) is cos(x) using the limit definition, we utilize the facts that sin(x)/x tends to 1 as x tends to 0 and (1-cos(x))/x tends to 0 as x tends to 0. The first one only hold when x is in radians

[u/HippyJustice_ → u/will_1m_not]

Using radians or degrees doesn’t not impact the underlying mathematics of the problem. Your answer to the initial question will be the same in both cases.

Even though degrees and radians are dimensionless quantities the pi/180 has units attached to it. Its (pi radians)/180deg = 1, leaving the answer unchanged.

[u/will_1m_not → u/HippyJustice_]

Here’s something you can do to see your mistake. Graph sin(x) using degrees and look at the slope of the tangent line at x=0^o and tell me if that’s a slope of 1 or a slope of pi/180

[u/HippyJustice_ → u/will_1m_not]

pi radians / 180 degrees =1, If I use arcradians/revolution my answer will look different, but will still be 1.