1 + cot2 ? = cosec2?. (2) tan2 ? + 1 = sec2 ?. (3). Note that (2) = (1)/ sin2 ? and (3) = (1)/ cos2 ?. Compound-angle formulae cos(A + B) = cos A cos B ? sin A
The identities. tanA = sin A. cosA sec A = 1. cosA cosec A = 1 sin A cot A = cosA sin A. = 1. tanA sin(A ± B) = sin A cosB ± cos A sin B.
Trignometrical Formulae sin(A + B) = sinA cosB + cosA sinB sin(A ? B) = sinA cosB ? cosA sinB cos(A + B) = cosA cosB ? sinA sinB.
For any complex number c = a + ib one can apply the exponential function to get exp(a + ib) = exp(a) exp(ib) = exp(a)(cos b + i sin b).
The “big three” trigonometric identities are sin2 t + cos2 t = 1. (1) sin(A + B) = sinAcosB + cosAsinB. (2) cos(A + B) = cosAcosB ? sinAsinB.
Fundamental trig identity sin(A + B) = sinAcosB + cosAsinB sin(A - B) = sinAcosB - cosAsinB. ** See other side for more identities ** ...
For example using the third identity above
sin 2x = 2 sin x cos x. Double-angle identity for sine. • There are three types of double-angle identity for cosine and we use sum identity.
sin(a ± b) = sina cos b ± cos a sinb cos(a ± b) = cos a cosb ? sina sinb Green's second identity: ???D(u?v ? v?u)dV = ???D (u?v.
If we were to subtract sin(? – ?) from sin(? + ?) we could derived the product-to-sum identity for the product of cos ? cos ?. sin(? + ?) = sin ? cos ? + cos ?