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Now, why don’t you find the other trigonometric ratios of 90°?, , ‘We shall now give the values of all the trigonometric ratios of 0°, 30°, 45°, 60°, and 90° in Table 8.1, for ready reference., , , , , , , , , , 2020-21, Table 8.1, ZA 0° 30° 45° 60° 90°, ‘ 1 Zo, sinA 0 2 2 1, A 1 4 an 0, “os 2 v2 2, , , , , , , , , , , , , , , , 1, tan A 0 aa 1 V3 | Notdefined, 2, cosec A | Notdefined 2 fy ry 1, 2, sec A 1 E 5 2 Not defined, ri, cotA | Notdefined VB 1 5 0, , , , Remark : From the table above you can observe that as Z A increases from 0° to, 90°, sin A increases from 0 to 1 and cos A decreases from | to 0., , Let us illustrate the use of the values in the table above through some examples., Example 6 : In A ABC, right-angled at B, A, , AB = 5 cm and Z ACB = 30° (see Fig. 8.19)., Determine the lengths of the sides BC and AC., , 5, , Solution : To find the length of the side BC, we will >", choose the trigonometric ratio involving BC and the ~~, given side AB, Since BC isthe side adjacent to angle B c, C and AB is the side opposite to angle C, therefore Fig. 8.19, , AB nC, , BC = tan, . 5 yore kl, Le., BC tan = B, which gives BC = 5/3 cm, , 2020-24